Nausea around girlfriend, doesn't go away after I broke up with her..

Hello Two months ago, I broke up with my girlfriend after a year and 3 months having a relationship. Ever since then I have been feeling nauseous, which is worse when i wake up. I wake up very early, and when i try to go back to sleep, I get very nauseous. I have to get out of my bed, or else it wont go away and it makes me vomit. Throughout the day, the nausea fades away. In my relationship I also had periods of nausea, but after a week or two they were gone. I always got nausous when I was with her.. After a while it became so bad that when my girlfriend asked me to do something together, I immediatly became nausous. My girlfriend and I thought that it was some sort of medical issue, so the doctor did a lot of tests, but nothing came up. It made us both very desperate. Maybe we were not meant to be, I thought. And I broke up with her.. It was one of the most hardest things I had to do in my life. I did not want to hurt her.. Secretly I hoped that my nausea would go away after our breakup but now, two months later, I still wake up every morning with nausea.. My ex moved on, she has a good life. Me, on the other hand, i'm still feeling miserable, and nauseous everyday. I do not want to get back together with her, I'm sure of that. I just don't know what makes me feel this way.