Sorry you are lonely. I always had difficulty making friends but did have some good ones even though I was painfully shy. Moving around a lot does not make for a lot of long relationships, either.
I probably would have done the same thing as you when friends were doing illegal stuff. Sounds like they were using you.
Having a life altering disease does kind of socially isolate a person. It's hard to make any plans because you can't tell if you will be able to keep them.
I probably talk to more people since I have been sick, than I did before, but most of them have to do with some branch if medical care.
You are doing the right thing by continuing your education. Maybe you will meet some nice people through that.
Best of luck.