Okay so my boyfriend and I have sex regularly and everything was fine in the beginning (february) and then I started my period and we waited to have sex again till after I got off of my period (March 12-16 btw) After we had sex I went home and used the bathroom and saw blood. I wouldn't say it was heavy but it was a good amount of blood. The next day we had sex again and I went home again and used the bathroom and saw blood again, it was lighter than the last time but still there. Then today we also had sex and there was blood lighter than the last two times. This just recently started happening. I don't know why. He is kind of rough during sex and I don't know if that could be it but he's always been kind of rough so why didn't I bleed the first few times we ever started having sex?? Is it just because my period and maybe there is blood still left up there and the sex is just letting the blood out?
You may not know this, but your uterus actively participates in sex. During arousal it lifts up inside your body cavity. During your orgasm, it contracts rhythmically. It is what gives you that very satisfying feeling and warmth deep inside you.
Your period cramps are partly cased by this same sort of contractions in your uterus wall, to shed the wall, break it up and expell it. It is just painful during your period.
So it is not totally unexpected that your orgasm can restart your flow shortly after your period ended, or even start it earlier shortly before your period starts.
Of course, it is also possible that you got injured and are bleeding from that. or he bruised your cervix and that is what is bleeding. It is just not possible to say here.
So when do you have to worry about this? If it does not stop, or it happens mid cycle or every cycle. If any of this happens, see your doctor to make sure everything is ok.