Bleeding During Intercourse

I have been with my boyfriend for 7 months. Just recently in the past two and a half months i have experienced bleeding during sex. There is no pain. The first couple times this occurred i was taking Alesse. It stops immediately after we are not having intercourse. I went to my gynecologist and he told me it was nothing to worry about and i should try switching to a different birth control. I then switched to Yasmin. After switching to Yasmin it did not occur for the next few times we had sex. I have not had a period or at least a normal period lasting longer than a day for two months, but im not pregnant. It started occurring quite frequently in the last month and half. Since then i have visited my gynecologist and switched my birth control yet again to a lower dosage called Yas. I have undergone pap smears for HPV and several std`s and the results have come back negative. While doing my pap smear my gyno explained that my cervix wall was exposed to my uterus therefore making it sensitive to the touch and closer to my vaginal opening. He has not been able to tell me what i can do to fix this or if there is a possibility of it going away eventually. I am becoming very frustrated with the lack of answers i am getting. He told me it was either an infection, my birth control or "a more difficult problem" . So far nothing has helped and my boyfriend has no interest in trying to have sex with me again until i can be sure that it wont happen again, So testing the waters is pretty much out of the question. Can anyone give me some advice on how to go about this, or has anyone experienced this kind of problem before?? I just want it to stop so i can enjoy a healthy sex life again.