I went through the EXACT same thing for two years, sweetheart.

I'm going to tell you what I did; I self therapist-ed myself and am now very optimistic. ᴖ ᴥ ᴖ I'm going to give you advice on the problems you stated. I'll write in
pinkAlso, feel free to PM me if you ever want to chat about anything ^u^
1) Most of my friends are calling me gross and running away screaming. I have no choice but to sit alone just about everywhere.
Well, are they just joking? Tell them you are taking them kinda seriously and ask for them to stop. If they don't, flat out IGNORE them. Tune them out. At least look like it if you really can not. When sitting alone, sit up straight and with confidence. Flash a smile at the person sitting next/around you and ask them whats up, or offer them food xD ("Hey wassup, wanna chip?") You might make a new friend ^u^2) My grades suck.
Ask for extra help or consider a tutor. I'm not accusing you of anything, but pay attention in class and ask questions. Plus, also remember that someone else is probably thinking the same question but doesn't want to ask. This well make you feel better ^u^3) I can't get a stupid honor roll at my stupid school because I'm a stupid person.
Honor rolls are not a mark of intelligence, just good grades. There are many kinds of intelligent people. And you are a different kind 
4) I just realized how many people are going to hate me for existing at all.
That's not true! D:5) I probably have very little keeping me going anymore.
Don't think that way.... When I wrote my sucide note last year, my cat came over to me and nuzzled me... she then walked over and pawed at one of my drawings on the floor. I cried and cried and couldn't believe I even thought about doing that. There is something worth living for in your life, but you may need to look for it. 
6) I'm lonely pretty much everywhere, and the only place I like to be is downstairs writing stories that suck.
I know what its like to be lonely in a room full of people. If you think your stories suck, try to improve on them. Keep the story line and such, but go through with details and do grammar corrections and what not. You can also get your English teacher to help; they LOVE helping students with their own personal stories. ᴖ ᴥ ᴖ7) I can't see myself having much of a job or a husband or kids of my own. I really can't see myself in 10 years.
Life is a journey, not a destination. I have no clue where I'm going either! It's a part of what makes life fun. It'll all unfold once it's ready too! 
8) I've gotten myself into a position in which more than a few people on CS think I'm insane, a liar, a very stupid person (true, though), that I have no life at all, that I'm in dire need of attention (not dire...but I wouldn't mind a little comfort right now...), that I've got no friends, that no one loves me or all of the above.
Well, surely these people have no clue who they are! They know nothing about you, where you're from, ANYTHING and they have NO right to judge you! Don't let them get to you. *hugs*9) My best friend hates my guts. (Okay, not Feather'sHelper or anyone else on CS)
I'm not going to be like "Oh, why are you hanging out with her" because I was in the same situation, except I was the one who hated them. I know it's complicated.
10) I'm probably going to get banned for posting this, but at this particular moment I'm too depressed to really care.
Don't worry, you wont get banned for ranting ᴖ ᴥ ᴖ11) I don't want to swear anymore. Really.
What do you mean by swear? Like promise? Or like, cussing? ^^;12) I've tried everything to make my life easier and it's not working at all.
Well, life isn't easy. It's hard and has it's ups and downs... But you gotta be strong and get through the downs. 
13) I think I've got no willpower whatsoever.
Neither do I, so I have no clue what to say *shrug*14) I can write really well, but no one ever wants to read what I write so I don't write anymore.
No, continue writing! Writing is a great way to release emotions as complicated as the ones you have now.
Ask your English teacher if they would like to read it. They enjoy it, trust me.
Ask him/her to make or not to make corrections. 15) Now that I think about it, writing stories is the only thing I'm good at. And no one likes it.
Everyone is good at something, but no one is good at anything. The only thing I'm good at is drawing, and I'm not even that good. And people don't need to like it because it's YOUR thing. Easier said then done, I know, but...16) I annoy everyone on accident.
Apologize and ask them to tell you nicely when you're getting on their nerves. I do the sammme thing xD17) There's only a few people who care about me, and that's only when they feel like it.
Their are people who care about you. But you might not notice. When I was in the very suicidal stage of my depression, my math teacher would ask me everyday how I was doing. I just thought he was creepy xD But now that I'm out of depression, he just smiles at me down the hallway and I'm like "Sup, sir!" 
18) I lost my pet bunny, who was the only friend who was always there for me, even when he was sick and before he died.
I'm so sorry for your loss D; I lost my dog Ringo a few years back. He was like a brother to me, so I kinda know what its like. To an extent. I'm not going to lie and say I do; my best friend, my kitty Meowth, is still alive.19) I'm failing in life so miserably that I doubt I'm going to ever not fail.
Nobody wins or loses in life. As long as you are happy. A happy nomadic person has a better life than a sad rich man. 
20) I sound like I'm whining...but I am. But I don't care about that anymore.
*hugs* 
21) I see no reason to keep trying anything.
Always keep trying, trust me, once you make it through depression, the world is so much better. I'm not exagratting when I say this: The colors of the world seemed more vivid and beautiful22) I draw kinda okay-ish, but... how's that gonna help me in life?
Many ways! Graphic Design and similar jobs are out there!23) I feel like a complete jerk to everyone and everything now.
No, you're not. You are NOT being a jerk. The world is being a jerk to YOU. *hug*24) I also feel stupid, ignorant and like I'll never be able to survive in the real world.
You will. Once this is all over, you will be a strong person.25) This is getting so long and I'm realizing so much that I feel like crying. I don't cry often so this is a change.
26) The only thing I'm succeeding in right now is making everyone mad at me and thinking I'm a horrible person with no life.
I don't see why people would think you're a horrible person! D:27) There's a lot of people on CS who hate my guts.
They shouldn't hate you! They don't even KNOW you!28) I'm a problem to everyone.
No, you're not. Don't think that way! D:29) No one seems to care about me much anymore when I need them most.

(great, now I really am crying. Goodie.)
Aw, dearie ;.; *hands a tissue* I know... I've been through almost everything you have. And some different things. 30) Most people call me ugly.
I'm not going to do the "inner beauty" routine, but EVERYBODY is beautiful, psychically, in their own way. You need to find how to flaunt your unique features. Try getting a haircut or dye...do your eyebrows and stuff. Instant selfesteem boost!31) I'm annoying people on CS who actually have lives.
32) Everyone laughs at me when someone insults me.
I'm so sorry ; ; 33) This whole list has happened since late February and I could keep on ranting forever.
Just let it out.34) I miss having something small and furry and warm to snuggle up with (my bunny).
;.; Sorry for your loss....I really don't know what to say. I think you really need a hug, but sadly, I can only cyber-hug you. *hug*35) I won't care if anyone hates me more now.
Don't let other people get to you.36) I don't care how people reply to this, I just want someone to talk to.
You can PM me anytime, I'll reply rightaway. ^^37) People talk about me behind my back all the time and they're nice enough to let me hear how stupid or annoying I am.
They are just petty and are trying to get a reaction from you. Try to ignore them, I know it's hard, try joking along with them, it might make them stop. I don't know, sorry.