My lover is a cocaine addict

So just need tips/ advice on how to go through this. So me and fiancé we’ve been dating for 3 years and we have 3 kids together. In the beginning of our relationship I was doing cocaine more like every weekend or every party and he would do coke too. So when we started dating we would do coke together but when we was 3 months in the relationship I got pregnant so I stop doing cocaine and drinking and after giving birth I breastfed my kids so I fall back on doing in my old ways. But for him he just didn’t budge to quitting and changing well in 1 point he stopped he was sober for at least a month then got trigger on doing it again because the friends he drank with does coke also and mind you ALL his friends do coke. We always have arguments on him doing coke like money wise and I guess the fact that he didn’t want to change his ways after getting a child and I was the only one who did. I told him many times that I can’t change him it’s all up to him if he can . But it’s getting tiring on arguing with him he does coke every single day. When we go out like with our kids he needs to get his fix made me feel like he needs to be high to be with us and I don’t want to feel that way. I gave him many chances and he gave me broken promises telling me “last one” but next day grabs I shed too many tears . I told him many times that he need to leave already I can’t do this to our kids I gave to many chances and he just doesn’t he just stays it’s like his not taking me seriously. I love him soo much and I tried and tired my best to get him better because I don’t want anything happen to him so I stay up with him just to watch over him. Honestly in my heart I don’t want to leave him but my babies is also what I worry about too. I know it’s hard to quit just like that but i told him before like slow it down a bit and make his way not doing it at all. I guess it’s all in the mind but i quit instantly especially when i was also heavy on it before but when i got pregnant with our baby and became a mom i told myself i will never turn back to that old self ever again. And till this day I don’t even have that in me. Anyone with the same situation or any tips and good advice would help? No judgements please I just needed to vent on here.