how do you tell your boyfriend you need sex?

yesterday my boyfriend was saying i was being moody which i guess i was.. he kept asking what was wrong, there was nothing wrong but this morning i woke up and realized i'm about to get my period on monday and i have those mini cramps... so i feel like it's hormones & i was moody because i need sex lol today & yesterday he was a little down because of me i didn't mean to be moody i just idk. idk if i'm making sense but how do i tell him? i miss him a lot too