Could vaginal bleeding be normal?

I have vaginal bleeding 90% of the time I have intercourse with my fiance. I am 23 years old and I have been to the doctor. She did every posible test for STD, cancer, hormonal, chemical, and pregnancy. Everyone resulted negative. She even ordered an intrauterine ultrasound, and there were no reportable conditions. After all this she said it worried her, she didn't what was going on and asked me if I wanted some anticonceptive pills. That was it. So, can vaginal bleeding after sex and between periods, and painless menstruation after sex be,after all, normal? I have always had an irregular 50 or more days light cycle period. Please help me this is very frustrating for me and my fiance. Is there a way to stop this? Will contraceptives pills help?

Although I cannot directly answer your question, I hope that I can provide some general insight: You did not mention how much vaginal bleeding you were sustaining after intercourse nor how long it lasted... is it just extremely light bleeding for a few hours, or is it more significant than that? Are you ever sore after intercourse? Does the bleeding occur both when the sex is gentle versus when it is harder? Does the bleeding occur after using some positions but not others? Are you keeping yourself well lubricated? Make sure that your vaginal canal is kept well lubricated during any penetration... with either your natural fluids or a product such as KY jelly (or both). Try to keep a diary of when you bleed versus when you don't... and record positions used and how rough it was. You can try process of elimination to see if you can pinpoint the trigger... for instance, if it only occurs in the doggie-style position, then you can consciously avoid doing it that way. My final piece of advice is that you can always get more than one medical opinion.. while this may be a difficult problem to solve, other doctors could generate ideas for alternative tests and/or treatment options which might not have been offered to you at first.