Bleeding after sex

Okay so my period is always on point like to the day I'm 8 days away from my period and last night I was having sex with my boyfriend and noticed some light pink spotting. Went to the bathroom a couple times and it was gone. Then this morning had sex and there was more bright red blood. We don't use protection just the withdrawal method. Anyone know what it could be! This has never happened before. I have no cramps or indication my period is here either.