What Causes Vaginal Spotting After Intercourse?

About a month ago my boyfriend and I became sexually active. I have had sex before, but for a lack of better words, my current boyfriend is much larger than my previous partners. Along with it being much rougher then all of the times before him (I apologize for how personal this is). We did use protection and he did not ejaculate in me (I am not on the pill though) and I also know that he does not have any STIs. A few days after the intercourse, I began bleeding very lightly. This bleeding occurred for about 4 days. My period was not suppose to come for a couple more weeks. We have had protected sex more times since the bleeding stopped. On the 22nd I was suppose to start my period, however it has not happened yet. Today and yesterday I experienced very light bleeding but nothing like how my period typically is. I was curious if I should be concerned about this. Also, I want to thank you in advanced for helping me.