Cheating, lying, trying???

Ok so my fiance and I have been together for 4 going on 5 years. We have a 2 year old daughter and we are well have been trying to make things work. He cheated on me last year with one of his old h.s friends and she knew that he was with me and we had a child. W.e anyway after that I broke up with him eventually we got back together then I found sexual emails between him and several women in his email he denied it until I said I wanted to get a lie detector test finally he admitted it was him when I asked why he said "he wanted to see what else is out there" this was 6 months ago we broke up and got back together now I just don't trust him I can't look him in the eyes I feel different I feel fat ugly etc and knowing he was talking to other women when I was pregnant back in 2014 I'm hurt. I gave him the world but yet even though I know I did nothing wrong why can't I be good enough for him??? I love this man he was my bestfriend he was there for my when I was raped and abused and cheated on by my ex he was there when my life fell apart he was my bestfriend now idk who he is :(