cheating

My So and i have been together for a little over 4yrs and in those 4yrs ive found out many times hes been talking to other girls he meets on instagram, and found out he cheated on me with his baby momma once (i forgave him and took him back) and these girls he txts never live in the same state that we do, keep in mind we have 2 babies and we live with my parents, im not the type of person to tell my parents everything thats going on because i dont want them to hate him either like if we end up ending this relationship i dont want them to keep saying things about him when all i wanna do is move on you know, so along the way i have been confronting him about every girl he has txted ( he has pictures of the kids and i on his instagram) and all the girls he has talked to know were together but i guess they dont care. Anyway when i confront him about it he goes like oh shes noone like shes not important, im like if shes noone than why are you flirting like that sending pictures back and forth i dont get it and his response is always get over it shes means nothing. I dont get an apology ever, so he stops doing it and talking to someone for a couple of months than starts up agin with a diffrent person im like wtf and the same shit diffrent day type of thing, i always tell him what if i did that to you and he goes like go ahead maybe you will find someone else. Oh and he also always threatens to leave us everytime he gets caught and i always tell him the door is open dont let it hit you on your way out, but he never really goes through with it because i think he has no where to go. Ok ladies i just need some advice on what to do if i should say enough is enough or should i keep trying please no rude comments i just need help