he wants to sleep with another girl

my boyfriend and I have been together for about 3 years..... the other day he was talking to his friends about how he was only with me and has never had any other sexual activity with another woman. His friends told him he should sleep around... So my boyfriend brought it up to me how I have with other men and he wants to be with more girls because it makes him insecure... idk what to do... I wanna stay with him but he wants to fuck other girl. Update!: so we talked about it I told him if that's really how he felt then it was time to leave because I could not be with someone who wanted that. And he said he was stupid and couldn't picture a life without me, and just being with only me is more than enough.