Timing?

My boyfriend and I currently just use the pull out method, no other form of bc. ( Not smart I already know but I don't need a lecture on that haha.)

Anyway, he thinks it'd be fine to cum when my period is due in the next day or two. I don't think so because I know sperm can live inside of you and I have a 21-24 day cycle so it's not long after my period that I ovulate. Opinions?