First of all, this isn't your fault. People fall in love all the time, and it hurts when things don't work out. Don't get me wrong; that it's normal doesn't make it any less painful; but the answer to "why" is most likely "because hormones are unpredictable, human beings are unpredictable, and you were unlucky enough to love someone who fell in love with someone else instead."

Suggestion: Transfer. Get out of that environment altogether. It is very, very jarring to do; but when you're attending a school where everything is too much to handle and there's no real benefit to staying, the best thing to do is just get out of that place while you still have your sanity. It's probably a good idea to do it before they consider kicking you out--both because you don't want to be tempted to get into another fight, and because, if they do kick you out, it will be difficult to find another school which will accept you.

If you cannot transfer, see if you can switch sections. Your courses may be taught at more than one time during the day. Large, single sections may allow you to sit near the door, come in just barely on time, and be the first to leave. You may be able to work it so that you do not have to interact with anyone at all--especially someone you may want to take a swing at.

Tell your psychiatrist your meds aren't working. There's no good just swallowing them down and hoping they magically start working; they've almost certainly got to be adjusted. This kind of depression is a relatively serious problem, and AS or no AS, needs to be addressed so you can get on with your life. If you haven't got a counselor, get one--meds aren't a cure-all, and if you can attack it from two fronts at the same time--biochemical and cognitive--you're far more likely to be able to shorten the duration and lessen the severity.