Akatsuki wrote:I get sad for no reason when I'm having fun, happy, or excited and I don't know why
Well, that can be caused by quite a few things. The most notable is Depression, however it could not be that. It could be caused by a flux in hormones, or tiredness, or being hungry. If you're not eating properly or sleeping well, then it can have an adverse effect on your health and overall well being. I would recommend a hot drink and hiding under a blanket with some snacks and watching youtube or a movie until the feeling goes. If, however, it's reoccurring, I would suggest talking to your doctor or parents about some support or just TLC.
Hope this helps
-Stu