boyfriend wont slow down on sex

OK so everybody probably wants a boyfriend who always wants to have sex but when we don't use condoms and I can't use BC because it messes up my body... we obviously need to do some type of slowing down. I don't know how to tell him we need to slow down though. I don't want to get pregnant and he doesn't want anymore kids so what's the solution? Can we stop having sex everyday three times a day please ! Plus my period is late I'm so scared.