How to cope with invalid emotions

A month into me and my SO dating we were having issues like initiating sex. We got over it but a month or two later I admired that the reason I didn’t initiate was because I felt like he wasn’t attracted to me and it was discouraging. I’m bigger and before me he always dated skinny athletic girls. He admitted to me that at first he wasn’t attracted to me and that really hurt but he assured me that now he was. Well I have free access to his phone and he’ll ask me to look at things for him and stuff but lately he’s forgotten to close out of his porn tabs and all the videos he watches are of tiny athletic girls and some of that insecurity is coming back. I don’t know how to handle it because I’ve never felt jealous over porn before or hurt about it and I feel like my emotions are clearly too much for what it actually is. Any advice?