Bleeding after sex?

[mmkthanks.livejournal.com]

 Before I went on HBC, I NEVER bled after sex, whether it was rough or not. Now that I'm on HBC, I can be "spotting-free" and the day after I have sex, I will start to spot and it won't stop until I get my withdrawal bleed. Could it be because my boyfriend finishes in me now? He never used to before, for obvious reasons. I'm just really confused because this has never happened to me before and it kind of affects my sex life. 

Thank you!