What should I do?

Lacie
I've been in a relationship with my boyfriend for 4 years. We love each other and push each other to be a better person. Well our sex life has always been non existent. We have sex maybe once a month. Same position. And it's in and out. He refuses to touch me. He won't eat me out or even finger me. I try and not to let this bother me because I feel selfish but recently I found him talking and exchanging naked pictures with a girl and I don't know what to do. I love him but I'm starting to feel like he's more of a roommate than a boyfriend to me.