Your situation may seem very bleak at the moment, but you can't give up, ever. Obviously you have something going on in your head that is putting a damper on things you need to do. You had that perfect school, but for some reason you didn't want to stick with it because of not taking your medication. One point of advice I can give you that I can never stress enough is to always take your medication. I'm bipolar, and if I don't take my medication, bad things happen. I can't function, and if I go to long without it, I have to be hospitalized.
Although the thought probably gets you very anxious, you absolutely need social interaction. It sounds to me though, like it's something you want. So you should be happy in a social situation because you're getting that interaction you desire. Now, since you probably won't be able to get into school, this means you need to either get a job or join a club of some sort. Or do volunteer work, anything to get you out of your room and around people. All things take practice, and you need to practice social interaction to get over your fear of it. I used to be really socially awkward, but I just put myself in social situations and I got the gist of it. So do try and find a job, you need to meet people
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Also, I'd talk to your doctor or psychiatrist about maybe switching medications or changing the dose if you still have extreme anxiety attacks, assuming you are in fact taking your medication. Like I said, actually taking it is very important. Also, talk to your therapist about these fears you're having, about being alone. They'll probably say a lot of the same things I did, but hearing it from a professional is often more reassuring than hearing it from a psychology enthusiast across the internet, i.e. me.
And, if you feel inclined, you can add me on AIM or MSN, whichever you prefer.