Is it time to walk away?😞

I've been in this relationship for eight years. My live in bf is still married after being together eight years. And every time I say the word divorce it leads to an argument. I've given him deadlines in the past and he never makes an effort to do anything. And here recently to make matters even worse. I just found out he has a baby on the way. I'm so tired of his BS I could blow a gasket. I really really need some advice on this very touchy matter. Walking away is easier said than done.