Yeah man, don't feel too down about it. You are just getting started. Keep looking for a job, look into some college classes (I can count on one hand the number of parents I've come across that mind having a kid who says "I want to go to college"), and if all else fails go buy the book "What Color Is Your Parachute" and read the whole thing, then do it.
I mean really, what did you hope to have accomplished by 20. You spent 3 years of it unable to do just about anything, then another 4 to 6 unable to do most of it by your self, you have spent (I hope) about 12 of it just learning the basics you need to survive. I've known a lot of people who "accomplished something" by age 20. Every last one of them managed ruin their future by either getting pregnant or arrested for drugs/alcohol. The people I grew up with who did have their heads on straight are now 24 or 25 and we are just starting to do anything with our lives.
Give it another 20 years man. If you still have no job, no money, no prospects, no education, and are living at home with mom and dad and none of that is related to failed business ventures, getting laid off (not fired), or badly maimed (like straycat), then you can consider yourself a failure.
BTW....Happy Birthday man.