First and foremost........go to the gym or run or do something that will help relieve some stress. Second....go see a counselor. You have had way to much grief to try to work through this alone! You are NOT responsible and your gf is a jerk for breaking up with you in the middle of all this stuff. So my professional advice (yep used to do this for a living lol) is to please go see someone to help sort all this out! The gf issue is one that I can't tell you why it happend, sure picked a horrible time for it. But maybe she can't deal with stress and what you are going through...she is young.
So.....1. Get active
2. Find a good counselor
So.....1. Get active
2. Find a good counselor