HELP! MY Boyfriend likes my friend!!!

HELP?

so when me and my bf broke up he wrote my friend asking were i was then it went to how horny he was..i got back with him and me and the same friend were playing around pretending we wanted a Threeway and he seemed REALLY into it...then later I asked him if he liked her he said yes. I asked him to scale it 1-10 he says a 5 and swears he didn't mean anything by telling her how horny he was a while back. What do u think? I feel crazy for being hurt by this .

Should I just leave him?