Yes. This happens. I am 35 and have a similar background to you; the identical thing has happened to me five times that I can count offhand and probably more. (Dropped out of CS, shut down a startup and laid off 2 employees including someone who is now BIG in the open source PHP community...)
The core life lesson I have learned (repeatedly): If what you're doing isn't working, change what you're doing. The HN world calls this "pivoting" ... it's not just a business term, it's something that you should constantly do as a technologist and a member of the generation you were born to.
You have done the following things that are not healthy:
- You have isolated yourself.
- You have given up on achieving something.
- You have apparently given up attempting to maintain good hygiene habits; hygiene is not just taking a shower and brushing your teeth.
As a result, you are suffering from depression and burnout. In an effort to get over the physical symptoms of burnout, you are consuming excessive amounts of stimulants, which help in the short term, but after the stimulants burn out, you're lower than you were before. You're actually burning yourself at both ends.
Fun fact: The physical/mental symptoms, like memory loss, inability to focus, dependence on stimulants to make up for cognitive deficits, and lack of ambitions are similar to what athletes (specifically, NFL football players) experience after repeated head traumas. You are literally beating your head against a brick wall.
Thankfully, you can probably recover from this. At least, I've managed it five times and counting, so that seems to be reasonable.
1. The first thing you have to do is quit your startup idea. Just drop it. Admit you've failed (at least for now), drop the mic, flip the table, and go in a different direction.
2. The second thing you should do is make arrangements to start taking college classes again. If you can, take classes at community college that will count towards ("transfer") a bachelor's degree. Don't go back towards computer science, though. Study a different engineering discipline if you can hack the math. I couldn't, so I headed for a business school and got a degree in operations -- we studied business logistics, supply chain, and industrial distribution among other things. (Go read "The Goal" by Eliyahu Goldratt. If it appeals to you, you belong in that discipline.) This is an example of fixing failing to achieve something by going a different direction. You're pivoting to being a student.
3. The third thing you should do is start keeping good personal hygiene. That means going to sleep at a set time every night (sleep hygiene). That means going for walks in the sun (fitness hygiene). Leave your cell phone at home. You don't have to go out at night, and you don't have to stop learning about web technologies, but you should make time to do other things with other people and with things that are physically present. (I have a dog, so we walk several miles twice a week and go to dog parks.) Role Playing Games (pen and paper kind) are excellent for this purpose. Clean the hell out of your personal space (apartment or whatever) and then keep it spotless -- this will ease your mind to an incredible degree. Start telling the truth to your girlfriend and parents. Admit, to yourself and everyone else, that you screwed up, but that you're going to make good on it. Ask for their support. Communicate with them; answer email even if you don't want to. Just don't lie to them or shade the truth.
(Hint: Your parents probably already know you're lying to them, and they're just waiting for you to come around.)
FTR - I'm a failed starter-upper, failed CS student, I've failed at being a boyfriend more times than I have fingers and toes to count on, I've failed to renovate a house, I've failed at my job a couple times, I've had a few scary mental experiences when I left myself alone too long with me, and I was failing at being a fiancée until a few months ago when I realized it was time for a change. New city, new place to live, new ways to spend my time, and suddenly I'm able to knock out my tasks for a week.
I am a Sysadmin/DevOps guy and an IT Generalist (I don't know it, but I can learn it), I am getting married this year, and I am buying a new house in a nicer city this year. I have three wonderful dogs and a fiancée I don't deserve. I would not have or be any of these things unless I had failed as many times as I did.
I wish you the best. Take a turn at the next intersection and see where it takes you.