first, please talk to someone about your depression. it's temporary, i promise.
second, companies/businesses that require or care about a degree or diploma are usually the worst. you had a high paying engineering job? well, that should be sufficient to get you into your next job, and if you sell them on who you are as a person/potential employee, even better.
third, you're only 20, and i know how that sounds, but it's true. relax. your life is just starting, and what you think you want or know now, is mostly going to change A LOT over the next 5 years. it might help to figure out some short-term goals, and go from there. we all go through rough patches in our lives, and you actually had the balls to quit and face a challenge head-on. this is something most people can't imagine doing, so it's easy for them to criticize others for doing it, which is why they're pathetic.
if i was 20 again, i would scrape together enough for a bus ticket to the bay area (palo alto, mtn. view, san francisco, etc.), and find a job at a startup. if that's not for you, then take the advice of others and get a job at a supermarket or somewhere just to get your brain on something else. then, focus on befriending people who were more like you, and decide what is best for yourself going forward, one day at a time.
some of us have been right where you are, and some of us know exactly how you feel. it will workout, you just have to ride out the rough times and climb your way back. no one on HN is going to judge you. as you can see there's a lot of support here.