I suggest getting some help. It could just be that you need to vent to someone like your girlfriend (which I would suggest first, because even if it doesn't help, I think she deserves to at least KNOW about it) or it could be something more. Sometimes something like medication or a change in diet/exercise can dramatically change your physical and mental health, and if it's affecting you to the point where it's making you sick, then that could be the issue. I just posted a secret called "I need to get back on track." Read it and see how dramatically a good diet, excercise, and medical regimen affected my life. Everyone's different, but it could work for you too.
Hope this helps :)