What Causes Vaginal Bleeding Post Intercourse?

Greetings. My main question is: is it normal to bleed during/after sex? Me and my boyfriend were having sex for the third time, and I somehow started bleeding a little, we noticed that on the condom. The first time (which happened about two weeks ago) was a bit painful and I spotted blood only about six hours AFTER the intercourse. The second intercourse (about a week ago) was a bit more painful, the pain was lancinating, but no blood during of after sex. And now, today, during the intercourse I felt that lancinating pain and then we spotted blood. I should mention, that my period is never on time and right now it s late for about 6 days, so I was wondering maybe it was the period, but the blood only showed up during and after sex and for the rest of the day- absolutely nothing and no pain at all. Should I get concerned about all this or is it just a temporary thing? Thanks for taking time to answer my question, I appreciate your help.