follow these 10 steps. this is exactly what i did to solve the same problem. of course our brains work different, but maybe, just maybe, this will help.
0. if you dont have, go get a job. it sounds hard, but its actually easier than it looks if you are willing to start from the bottom. i just appeared at the kitchen entrance of a restaurant and straight out asked if i could wash plates or something like that.
1. go hit a shrink
2. tell him all, and i mean all you can. the more you talk, the more they can help. they wont judge or laugh or tell the cops, they are there to listen to you. they generally try to find patterns or causes in your actions, and make you think about it, BUT the most important part of modern therapy is to hear yourself saying what you think out loud.
3. start some kind of hobbie or recreational activity that cant be done from home. maybe football across town, or a photography course somewhere, but dont do it at home. go outside to do it. this is to get to know people. dont feel shy or stupid or ugly, people there share the interest and wont bark at you from day 1.
6. wait. its never late to start that career or at least finish school.
7b. if you start to find yourself having some free or spare time, occupy it with something. try to avoid things like tv, social networks or vidya; replace that with some productive activities. working on some project, contacting forgotten family or friends, going to the gym; whatever keeps you from isolation and degradation. of course some days you just want to lay back and watch sopranos, and thats ok. but try to keep your mind active.
8. idk how's your job or situation by now, but thinking about that long lost girl now seems different. maybe the shrink didnt help at all; but you cant say you tried. all these things take time, you cant tip over your whole life in a month.
9. wait some more
10. keep maintaining yourself busy until you die. its the only way to cope with the sensation of never ever satisfying the ambitious demands of the mind, no matter how much control of your physical reality you have. maybe you already fuarrrked the girl you wanted, or got that dream job where you listen to trap music and just wave your hand to it to test its swagness. but you will never be comforted, completed, full.