Emotional sex during my period

Ok, so my bf is a freaky boy, he like having some nasty(but fun) sex stuff. A few days ago we were both super horny, but I was on my period, he said he didn't care. So we start doing it , and honestly it felt pretty amazing. But there was a point where I just burst into tears for not fucking reason. He's confused, I'm confused and embarased. He gently takes me to the shower and we take a nice warm shower together, he hugs me and I cry it out. I don't understand why I started crying when I was enjoying everything.