Is masturbating to porn when you know your SO doesn’t want you to cheating??

For the 3 years that we’ve been together he’s told me that he didn’t masturbate to porn because he had me and also he knows that I’m very insecure about my body so I don’t really like him looking at other girls. It took me a while to even get comfortable being naked with him. I was molested as a child so my body is a sensitive thing, if he’s looking at me I want him only looking at me. Well I believed him when he told me that he didn’t need to that and it made me feel better and relieved. But last night I found out that he actually masturbates to porn and it really hurt. I just don’t know how to feel about it, he’s lied to me for 3 years about it. I know he hid it because he didn’t want what we went through last night to happen. He said that he didn’t want me to see him as disgusting and he didn’t want me to think bad about myself because of it. I can’t seem to get the fact that he looks at other women for pleasure out of my head and it’s driving me crazy. It’s all I can think about, I can’t get the image of him looking at other girls away. I feel sick to my stomach and I just don’t know how to handle it. I’m trying to be okay with it, but it feels impossible. I feel like he chose them over me to please him. He said he only did it because once we wouldn’t have sex for a while, his balls would hurt, (Is that true?), so he would only do it about once every two to three weeks. I really thought I was the only one he looked at, heck I thought I was the only one he wanted to look at. He said that whenever he would watch them he would think about me, but I just don’t know what to think. I’m just hurt and I don’t know how to handle it or how to feel. I don’t want it to bother me, I just need to know how other ladies see it and what they think. So if you don’t mind, please comment how you feel about it and why.