I am going through the same thing! I have spotted a few times after sex and then Tuesday I bled during sex and I should have started about a week before that so I thought I was just starting, but then it stopped.. and I haven't had anything since! But now the last two days i have been having cramps so I am hoping its nothing and I will just start already. I'm really worried that it is something else! :/
Hello,
This condition is called post coital bleeding. It is most commonly seen in vaginal infection like Chlamydia, gonorrhea, vaginal inflammation etc. it could also be due to disease of endometrium that is lining of uterus, polyps (mass) in uterus and cervix, fibroid tumors etc. You should consult an expert nearby for internal examinations.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.