orgasms make cramps go away. lol.
If i'm on my period and we have sex, he wears a condom so he doesnt get blood all over his thing. and we do it in the shower. (easier too clean up after) If you want to do it in a bed or wherever, put an old blanket or towel down so you dont get stains on your nice sheets.
but it all depends on if you BOTH want to do it, you might be fine with it and he might think its nasty.