What to do when you’re in love but not happy

My boyfriend and I have been together almost four years and our sex life has been declining the last two. Now we have sex monthly, maybe. I tell him how I don’t think it’s fair at all to me how he just doesn’t try, he knows it is a problem for me. He’s 24, I’m 21 like we just moved out and have had sex 15 times since August. I’m honestly done, before we moved out it sucked and he said it would be different when we move because it’s our own place... not different at all, it’s honestly worse. Idk how much longer or what else I can say to relay how much I hate it he just won’t listen. He won’t even try either, I suggested msybe his testosterone is off or maybe he’s depressed but of course there’s nothing wrong. & to top it off he has been watching porn instead.. though we both agree it’s a no for us. I don’t wanna break up with him because of this but I feel like I deserve what I want or a little effort at least. There’s nothing else wrong with our relationship the intimacy just is gone now.. can this be fixed? Is it unfair of me to leave him because of lack of sex after 4 years...?