I'm so so tired

Tired of arguing, of his negativity, of him continuing to put me down. Yet I keep going back and looking for him. Wondering if hes ok. We have a 3 year old and have been on and off ever since she was born. I kept blaming myself because I was the one that cheated when she was about 4 months old. It's been a rollercoaster ever since. I think it's just better I walk away now. We are both 27 and it just feels like I cant keep beating a dead horse.