Can cum block your period?

Abbey
Okay, I know I'm probably over reacting, but I just wanna be sure. 
My bf and I had sex two days ago and he came inside of me, I'm supposed to start my period today and I haven't yet which is weird because I'm on the pill and I've never missed a day, and I've always taken it at the same time. Just wondering if it's possible that his cum is for some reason still there and is blocking my period from coming out? Has anyone else had this issue?