Should I stay?

i have been with my boyfriend for 2 1/2 years. i thought everything was going great, we had a baby together he’s 6 months, i love him, he loves me?well when i was leave for work after i had our baby boy he told me he had cheated on me and has another baby with some other girl. this baby is only a few weeks older then our son. he told me it was one time thing and he was crying and very sorry that i was the one he wanted to be with. so of course i stayed with him.

this girl i work with knows the other girl that has the baby. i have talk to the this girl i feel like she hash no reason to lie to me. so i believe every word she says about him trying to be with her the last year and a half. i ask him about everything, he tells me that none of it is true, he told me that she is just trying to break us up? but you see i have caught him and that girl in lies. so i don’t know who to believe, because it took him a whole year just to tell me he has cheated. i had asked him way before i had our baby if he has done anything else with anyone, he told me NO. he said he would never do that to me because he loves me so much. i need some good advice for what i should do? because i love him alot, but i am also very hurt too