Why is it tight when on period

So this guy was trying to hook up with me last night and I told him I was on my period and he was like ok that’s fine and I was like ok if ur down I’m down so we tried putting it in but I was supppper tight, tighter than usual and mind you I haven’t had sex in a while but I was a bit concerned if it was just my period that was stopping him but like we just gave up and I was really embarrassed