He cheated..

I’ve been dating this guy for a couple of months and i’ve sincerely fallen in love.. until tonight he called me to tell me he made a mistake and was texting another girl and he ended up getting carried away. they didn’t do anything in person.. it was all over the phone. Me and the girl talked, so I know this is true. but i’m hurt, really hurt. I don’t want to lose him but.. i don’t want to just forgive him. what do i do?