I caught my bf watching porn

So my boyfriend has been getting mad at me lately for no reason and he keeps bringing up my past which he says i cheated when we had broken up for 2 months but he still says i cheated and the guy i was seeing called him from my phone and said we were having sex and from there it went down hill so after we had gotten back together he says thats all he thinks about and its been a year now and he would tell me everyday that he honestly cant get over it and he cant be with someone like that and that he loves me but he is not in love with me and just yesterday i had left to my moms house and i came back to his house and he locked the door and i had the key and i walked in and he was laying down and had his ear buds in and he hid his phone under the blanket anf i said your watching porn arent you and he just nodded his head yes and he got up and walked off and said why are u watching that he just said because i want to and it just broke my heart but its not the first time this happens ive caught him like 5 times already and i just want him to stop but im not sure if he will , do you guys have any suggestions??