Only just seen this, didn't want to read and run, the positives here are that you recognise somethings not right, and that instead of giving in/up at situations that you have found hard, you haven't and still have pushed yourself i.e. not wanting to go into work.
The best thing you have done is ask for help, from professionals. If you feel the need to cry, do it, wont help to surpress it.
In some ways, and please don't take this the wrong way, it could be a good thing in the long run that you have split with your girlfriend (it doesn't make the pain any less) you both deserve for you to be well and sorted in your mind before embarking on a relationship (being she's only 20(?) she might not have had the maturity or inclination to support you through it)
Don't torture yourself trying to work out how or why your feeling like this, you'll drive yourself mad, just concentrate on the positives (which there are, even if you can't see them, or they are small) and getting better, best of luck, theres always a listening ear on PF

Z