Im not wanting sex but he is

Hi ladies, my boyfriend and i arent having sex very often and he is wanting it. I work 5 days a week so im very tired after work and my boyfriend is always in that "mood" and im not. I want to plesure him but im not going to have sex if im too tired otherwise i wont enjoy it. 
Im even too tired to give oral or hand. And on my days off i dont even feel like sex. 
I dont know why. I love sex but the last couple weeks i just havent been in that mood for it but he has. The last month we have only had sex once because i just haven been in the mood for it. 
What do i do??