Crying during/after sex?

I don't normally cry after sex but lately when we finish he always pulls me close and holds me for a while and since I'm always on his chest I can hear his heart beating.. Lately I've just broke down in tears and he's tried to console me asking if he hurt me or if something it's wrong but that's the thing I have no idea why I'm crying... I just stay quiet and try not to me make it noticable anymore cause I'm embarrassed he thinks something is wrong when there isn't anything wrong. Any ideas as to why I break down and cry?