Trust Issues...

Ke
Me and my boyfriend have known each other since high school we also dated for one year and half during that time. We took a two year break thinking we were not meant to be and somehow ended up back together in 2014. We have been together ever since and there have been so many trials and tribulations from the beginning. When we first got back together to me everything seemed fine. We were in that fresh beginning stage of the relationship where everything is so sweet and lovey dovey. Skipping all the small details a year later we moved out of my moms place and got our own. Everything once again in my eyes seemed perfect until after almost a year of being in our own spot things started to take its course. (Now mind you within our two year break he had a break baby and was with his BM in which was supposedly crazy. So he picked up some bad habits that he's been having a hard time breaking) He started to become very distant and was pushing me away which was something I was not use to. This went on for weeks and during that time I found comfort in talking to this guy I meet online. The guy was married and was experiencing some of the same things I was experiencing. We started to become a little intimate through social media.. trying to fill what we was missing from our significant others and knowing I'm terrible at talking to more than one guy, I got caught. My boyfriend was so upset and made me feel like the worst person in the world but later on that day I was on my laptop(which we shared) and I saw his email up........ he was talking to other females. Not starting on that day but long before that. I was pissed thinking I was the bad guy and he's been going behind my back the entire time. I kept it to myself and eventually it came out. He claimed he was doing it because I messed up but that couldn't be the case if this was happening before I did what I did. I just left it alone. A few months later I found out I was pregnant(it was planned because we both had been trying for a year). I was thinking maybe this will help our relationship and bring us close. However the situation got worse. He was not working and was talking to females right in my face. He was so careless and I was sooo stressed. I was hoping for a miscarriage because I didn't want to bring a baby into a dishonest relationship. I tried talking to him time and time again. He said he would stop but never did. My whole entire pregnancy was full of promises, lies and tears. Even the day I gave birth he was messaging other women. After having my daughter Delilah I found a video that he sent to some female and that was my final straw. I was prepared to be done with everything. Me and him talked and I told him how I know about all the bullshit he's been doing since 2014 and I've been putting up with it and it's 2017. I told him that I loved him but it will be hard for me to ever trust him. Ever since that talk he made up in his mind that he was done, he won't hide nothing from me and he will change because it's not a good example for our daughter. I believed him but every now and then I have my doubts. It was January 2017 when we had that talk and recently I went through an old phone of his hoping I wouldn't find anything. I didn't find much but a convo he had with a girl that was an "old friend" and a deactivated plenty of fish account. I asked him about it and he was upset with me for even thinking he was messing around but he don't see my point of view. Since all this mess have happened I am very insure and my trust from him is low. I want to make this relationship work because I can't see myself with anyone else and no one gets me like he do but how do I move forward? How do I learn to trust him? How do I learn to be comfortable with him holding a simple conversation with another female or leaving the house without feeling insecure? I would like some advice ladies. I don't want to screw up my relationship because I'm always in my head thinking the worse. Whats something me and him could do to better our relationship? All advice is accepted. 
If you made it to the end of this... Thank you for reading this. I appreciate it.