I think you're just lazy.

It's your own fault for the position you are in with your college. If you want to transfer schools and get better grades, then you're going to have to wake up and go to class. You said you picked a few wrong classes. That's fine, you can make them up next year. Possibly take summer courses? Correspondence?

A good way to make friends is to get a job (if you don't already have one). It's a good way to start, especially if it is in a kitchen or a place where you wear a uniform. You all meet wearing the same thing, not alcohol or drugs to get in the way. You can make friends with people and really get to know them.

You say your friends are better off for having the opportunity to party.. but you have that opportunity too. Put yourself out there, talk to people. Don't just go up to someone and ask about parties, work your way up slow so they know you want to be friends with them. There are plenty of people (at my school) who don't drink or do drugs, and they still are able to party, because they don't need drugs to have fun.

A reason you may not be invited to parties is because they might expect you to mope around and not party. You can be sober and still party! You need to try a little harder. Try texting your friend, see what they say. If they don't reply, then no big deal. At least you tried!

You are already judging your friends for something they didn't do.. You don't know that they will think it's weird if you try drugs or alcohol. If you want to try them then I'd say go for it, but if you're doing it JUST to fit in, and not because you want to try it, then don't. If you have something against it, don't try it. Or you'll be just as hypocritical as you think they are.

If you really do think it is depression then you should go see a psychiatrist, but I think you should try a bit harder first.