need advice

So the father of my child and I have been together for almost 2 years now. We had our daughter in June. I found out 2 months back that he had cheated on me the whole entire relationship, including the pregnancy and even 2 months after our daughter was born. I am so lost on what to do, he swears up and down it was a mistake and he won't ever have an affair again. I'm so hurt still. I just want to know what your advice would be and if you've been in a similar situation how it ended up.