What Causes Vaginal Bleeding During Intercourse?

after intercourse I have abnormal bleeding that may last for days at times. I consulted oby/gyn and she said this problem was caused by a thick lining and it needed to be broken down so she prescribed provera 10mg pills. After 8 days I had a heavy period that lasted 6 days. The day after the final dosage I had a light menstrual that lasted 5 days. A week later I had intercourse and the same problem occurred; I began bleeding after intercourse. Can you tell me what is the cause of the problem and offer some solutions?