I went through something exactly like this. Well, not exactly, and nowhere near as intense, but something very similar.

This may come off as bad taste, but “cutting off” is actually the correct way to go. In fact, the earlier you’d do this, the better. It’s been 4 years now, and I’ve been happy ever since. Never had a drought of depression.

It sounds scary, but the key to not falling into a helpless, depressing abyss is to occupy your mind. Try mundane things; you have a summer job now, that’s a start. There’s an endless amount of shows, cartoons, movies, video games and music to explore. There’s a whole slew of hobbies you can try. Drawing, animating, composing, programming, reading…

Also, realize that you are so fortunate to have so many people who care about you. The kind of people you spend your daily life with and never feel this sort of doubt. The kind of people you might not talk to for months, maybe years, but come back to and talk with as though you’ve never been apart. They will always be there for you.