Something is wrong with me?

My boyfriend and I have been sexually active for almost 2 years now. At first, I had a super high sex drive that just about equaled his and we would have sex at least 5 times a week . Now I barely even want to have sex once a week, and when we do have sex I feel overwhelmed and start crying. Should I be concerned/see a doctor? I have no idea what's wrong with me. I'm only 20 years old...