Still looking......

My boyfriend and I have been together for about 5-ish years..... maybe more not sure. Anyway, a year ago I found out he had been looking at BBW's. I have no issue with big women, it just it makes me insecure being that I can't gain weight even if I wanted to. When this problem first occurred I told him that and I asked him to stop. And of course if he did I wouldn't be telling this story to a bunch of strangers so they can judge me. Well I saw he had been looking again and I got upset, because this has happened a couple of times. He kept asking me what was wrong and I told him obviously how I feel doesn't matter and kept saying he didn't care. I didn't feel the need to tell him why because he knows what he has been doing. and he even asked me if I was mad because I found something I didn't like in his phone so now not only do I know he is still looking at BBW's, I feel he is cheating. I saw part of a message when I was exiting his apps and all I saw was " I know you don't know me but I just wanted to tell you......". i just want to know what to do how I should go abot this . I love him but I don't trust him and it's got to the point I don't care about us at all.