I use the depo shot for birth control and i

Patient: I use the depo shot for birth control and i have been on it for about 3 years. i have not had any problems with it until just recently. I just received my shot in late April and about a week after that my boyfriend and i had sexual intercourse. After we where done we realized that i was bleeding very heavy but it only lasted for about an hour. We thought maybe it was just because of irregular periods. The next few days we decided to try again and this time i did bleed but it was very light and a very pink color and did not last very long at all. What causes this?

Symptoms: Irregular bleeding after sexual intercourse and even after masterbation

Doctor: