sexual pleasure

Hayden 😊😘
I've seen a lot of posts in my time here about women who either don't enjoy sex, barely get pleasure from it, or can never orgasm from sex. 
I fit into this category, and it puts a huge strain on my relationship. Since I never get anything from sex I almost never want it, which is a problem because my boyfriend constantly wants sex (of course, because he actually enjoys it). 
So I wanted to ask all the ladies in the same or similar situation: how do you handle your sex life if it's no good for you? It can't be selfish to just not want to have sex when you get nothing from it, can it? Do you just do it anyway because your SO likes it? Do you idly allow it to happen when they try? Do you participate fully and just not get anything from it? How do you handle the emotional aspect of sex just not being good?
These are things that are constantly on my mind and I need some sort of reassurance or advice.