I need some opinions

My boyfriend of 4 years was obsessed with porn, i didn't mind him watching porn now and again but he was doing it every time i wasn't around, even when i was sleeping. For a while now he kept saying that he's not watching no more but i knew he was. The thing is, he was always watching transsexual porn which i found it to be weird and i confronted him about it and he said he is not bisexual or homosexual. I'm so confused because in the beginning of our relationship we had a great sex life, now i'm the only one that wants to have sex but he is always tired, or stressed or something.

This morning i was staying on the computer and one of the last searches was: "transsexual men" on one of the sites for escorts in my city.

I really don't know what to do about this.

Sorry for the long post and my English, it's not my first language...