As a medical student, I see this issue come up time and time again with my fellow classmates and friends. The road you and your boyfriend chose is definately going to be a long and difficult one. With that said, I think that if the two of you make it through this period of time, you will have a stronger relationship in the end. There's certainly a ring of truth to the high divorce/break up rate during medical/dental school, however, I don't think that the school is the cause. I believe that the intensity of school only magnifies the issues that underly your relationship already. People that breakup during school, would of probably broken up anyway. The school just speeds up the process.
Once you start your own classes and make new friends (basically have your own life/interests) then things should get better. For women, it's so important to have a sense of independence. Have a life outside of your relationship. Do things that make you happy. You can't change him, but you can change yourself and how you react to him. I'm sure that he must be a wonderful person in order for you to move for him. So, be patient and understanding. And if all that does not work, then, it's not meant to be. But you will be just fine with or without him. 🙂