Oh gosh. I'm 45 now, probably a good deal older than most of the people who post to this site, but I empathize with you. I was your age when I dove into living abroad and working in a refugee support agency, far on the other side of the globe. On the flight to the agency, I was elated and, as expected, it was an astounding experience for the first four months. By 8 months in, less astounding. By 10 months, sheer freaking hell. I had no friends, I was working 15 hours a day, I was exhausted, I'd started to hate the other agency workers, I was the only person my age that I knew, and I'd started to resent the demanding neediness of refugees (I KNOW, right? Refugees! That's how bad it had gotten).
After a very bad night of weeping and drinking, I ended up in a religious counseling office. I am an atheist. But that was the best damn thing I ever did because the counselor listened to me and then said, "If you don't call your parents and get a plane ticket out of here, I'm going to arrange to have you medically evacuated for depression and anxiety disorder. That will be embarrassing for you (pause). What would you like to do?"
I quit my internship and went home two weeks later. Within a year, I had a prescription for an antidepressant (which I'm still on, BTW) a great part-time job, was in graduate school, and met my current spouse. All before you were born!
So I'm old enough to be your parent . Here's what I know. The twenties are terribly difficult time of life for many people. You're in a post-college transition phase, moving into adulthood with all its attendant complexity and responsibility. You shouldn't BE alone - yet. It's actually much easier to make that transition if you've got friends and a job because transitioning to adulthood is easier when you've got the social, financial, and organizational infrastructure to help you become a professional and an adult. You need to build that, and your instincts about getting a regular old job are dead-on.
Here is my advice: Do exactly that. You've gotten everything you can out of this experience and you've learned a lesson about your need for social interaction, despite your inclination to be reserved. You're obviously talented and entrepreneurial and I expect plenty of companies would find that a big plus in a 22-year-old hire. Get your resume together and start looking for that job. Get yourself a mentor and ask that individual how you can spin your entrepreneurial adventure as a killer aspect of your resume. If you've got IP that you feel you can sell, go for it. You can also keep your startup as a side gig, if you'd prefer - just make sure your new employer is on the up and up.
You are not a failure. You have not failed. You are not stuck. You are skilled and articulate. You're brave and have had tremendous success for a 22 year old person. You will start feeling better as soon as you submit that first resume.
As you get older, time passes by more quickly. It's a bizarre feeling. That's when you begin to realize that life is really very short. Work is only part of life. It's most gratifying when you've bounded its presence in your life - when you set it aside to enjoy a glass of wine with friends, to go for a long run or doze outside on a sunny autumn day.
It is time to wrap up this experience. Pull up that resume file, now, and start your new life.