Finally walked away but...

How do you walk away and stay away?! Any tips? I have taken him back multiple times in the past and this time it’s a different feeling. A feeling that just won’t allow me to go back but I’m fearful that I will somehow end up back with this person . I don’t want to be with him he cheated on me so much and I’m expecting both of our first child. It’s so hard to walk away and stay away when you truly wanted something to work and it just won’t. I hope what I’m saying makes sense. I’m open to all advice even if it’s harsh. Maybe that’s what I need to open my eyes so that I can stay gone