Pregnant and cheated on

So I just found out my husband cheated on me. He was sleeping with another woman for a long time. It wasn't consistent but was a handful of times. I'm pregnant and we tried for our baby for a long time. He claims it started when we were in a rough patch which we were because I found out 6 years prior he had cheated before we were married. It was a one time thing and we were working through it. I decided to try to work it out because we were married now and he was going through something when it happened. Shortly after finding out about it, he began to cheat with this other woman and this time we were married. We really didn't work through what happened the first time just kind of fought constantly. Well he started that affair and then things got better and we worked through our marriage. He said he tried distancing himself from her but she threatened to tell me so he continued (dumb I know). Then we tried having a baby. We struggled and seeked fertility treatments and finally conceived. We were so happy. Well he tried to stop even more but she threatened again. He said their visits limited. I am so hurt that he could do this to me again and our child! The worse part is he didn't use protection. He swears he is sorry and has been crying constantly. He says he will do anything and is so mad because he began the affair before things were good and mad he messed that up. I said I didn't want to work through this pregnant. I won't do it again. So I'm kind of in limbo. I don't know what to do. He wants to go to counseling for himself and our marriage. I need help deciding what to do. If I wasn't pregnant, I would be gone already. I have been crying every day since and can't believe this happened again. How do I trust him ever again? I can never forgive him for doing this to our family. How do I know if he's serious this time? Is it possible I don't even know who he is. We have been together a very long time but married a few years.  Sorry this is so long. Please help!