How Do You Change?

I've had a very hard past. I've been through abusive relationships and always been the one to take the blame. My first boyfriend abused me in everyway possible. The next was my husband who cheated on me for 2 out of the 5 yrs we were together. Then my sons father came into the picture and expect me to take care of our family as far as working and raising our son. He wanted his porn and dating sites over anything, his computer was his family. All of these relationships I ended with the hope of meeting one guy who was worth my time and energy. For 2 yrs now i've been in a relationship with a great guy. He works hard, we have 2 houses together, and hes stepped up and been a father to my son. Given my past and the things i've gone through, i find it hard to trust anyone and to just relax and appreciate having what I have now. I'm so afriad that its all going to end the same way. I knew he looked at porn but when we got our computer I felt as if he was taking care of himself more than wanting to take are of me. For a yr we fought about the subject and had many knock down drag outs. It was hurting me because I don't have even the smallest ounce of self esteem because of pervious issue. This is something he couldn't see and i did the worst thing possible, I cheated to show him the pain the I had been feeling for so long. The wrong way but it did allow us to finally feel each others pain.and allowed us to talk more openly. This happened six months ago and his use of porn has seemed to slowed down and he seems more in touch with me. It's just now I can't get over the porn everythime I find it its an arguement and fight on my part. I know this is a natural thing for men to do and i know its fine as long as the other person is still getting there fulfillment. I just can't let it go and keep the understanding that its okay. and he doesn't do it when i'm around it just when i have to leave eaily for work and hes by himself. I just need help in getting my self esteem back and getting okay with this issue. He does love me and I know that he would never have taken me back after what I did if he didn't plus he shows me everyday. I need advice on how to just relax be happy get my confidence back, and just be okay with the normalness of something every man does