LDR's are rough and hard to maintain. They can succeed, but they have a higher chance of failing. She just made an independent decision that long distance wasn't working for her and that she wasn't invested enough in the relationship. It's certainly better than ignoring her own feelings and continuing on, because then you both just end up being miserable.

This break up is an opportunity to find a relationship that can work. You've already shown that you can find someone, so it stands to reason that you'll be able to find someone else. Either way, if it was meant to be you'd both still be together, but now instead of both of you being miserable for decades you only have the temporary pain of a break up to deal with. Which still sucks, believe me I know, but it gives you the chance to find someone who makes you happier and gives you more reasons to keep going.

As for friends, I don't have that many either. Funnily enough, most of my friends are long distance and I rarely see them, but I'm more of an introvert so it suits me a little better that way. I can get overloaded on people sometimes. While you might have barely any friends, you still have some. You don't need many, just a few good ones.

Because of my depression I've been withdrawing myself a lot and my conversations with her had started to become really mundane and boring.

To me that sounds more like a relationship that had begun to stagnate. Which isn't your fault, nor hers. Unfortunately distance can do that, regardless of Skype or phone calls.

I'm a lost cause.

I don't think so, or you wouldn't have found a girlfriend or made any friends to begin with.