Hey Sanai,
It's really crap to hear things like that. No point pretending otherwise, I know you will be pissed off.
As I've said before in other threads, best thing I can really suggest is talking through it in detail with someone. The next step is also trying to look at things from both sides. By that I mean things like:
I am failing the course I am
Try and think and look at it from another perspective.
Am I failing because I can't do it (doubtful from what I have seen of you, you seem intelligent) or because I am depressed and not putting in the effort. If that is the case this is something you can actually change, it is not the dead end you might think it is, its just a rut you can actually work your way out of.
A lot of things that may be bothering you, if you try and sit down and think about, however hard that might be, you can generally work a way around them or fix them. It might be a long term thing, it might require effort, but at least you know there is a way up. Doing this always used to make me feel better.
Also think of things which are good: You're healthy. You're intelligent. You've got a good personality, very caring, great humour, perverted (a big bonus in my eyes), creative (shows in the RPs) and insightful. This is shown just from the forum, so there is probably loads more.
Finally in regards to the girl.......I won't lie, its bloody hard. First thing I would do, as hard as that might be is to make sure. The thing which drives people insane is always wondering "what if". I did that for years in High School and I look back now and realise how much time I wasted (yes even the great Perverted One got rejected

). Once you know for definite then you can start trying to move on.
If she really doesn't want to be with you, hard as it may be you need to sit back and again think or talk to someone to help move on. It happens to all of us, really. It does not make you any less of a person, it is not anything bad against you, some people just don't have that connection. But there will be someone out there who does have that connection, and its much better to be out there looking and see them, rather that hoping for something you can't have.
You said it is a girl. Well for me that would be some consolation, in that it is definitely not a matter of you personally, but the fact she prefers women. You may find in this regard your friendship still can and will work as the mechanics of having that type of friendship is much different than a normal hetero one. (I say that from experience with previous lesbian women I have known.).
Hope that helps somewhat Sanai, but if you want to chat just let me know.