I am so fed up with my son!! Advice needed?

I am so tired of my son! He is 20 years old and acts like a child. He graduated but barely. He hasn't had a job since. All he's ever done is play on his computer and talk to his online friends and read anime. He doesn't know basic needs or how to balance a checkbook, he's bad at Math too. I think he's depressed and always struggled with it. He has ADHD and stopped taking his medication years ago because they made him emotional and sick. He has tried a special medical school where it's a little easier for people who aren't as intelligent. Anyway, he says he doesn't mind getting a job but he's too anxious about working. I think deep down he wants to better himself but he's negative. He told me before medical school that he wouldn't like it and it wasn't worth the money. And he stopped going it within 2 months, and now I'm stuck paying 2000 dollars for his schooling that he's not even doing. He doesn't care about ANYTHING. If I kicked him out it wouldn't work because he just says he'll just live homeless and still not get his crap together. Our family is always asking me what he's been up to, and then they all talk about him like he's a loser. All he talks about to me is some comic book character and how pretty he is, and I am tired of it. I admit I wasn't the best mother, I was young and neglected him often. But, he isn't my responsibility anymore. He's an adult and I love him because he's my son, but what am I supposed to about him? What is wrong with him? Is he mental?