Not wanting sex! 😢

Hey ladies so I have a situation, I'm living with my boyfriend. We've been living together over a year now, the issue is he always wants to have sex and I'm never in the mood! Before we used to have sex all the time, but now I'm either too tired or just not into it. Idk what to do he's already asked me twice why I never want to do it and I honestly don't know what to tell him. Any suggestions would be great but please no negative comments. Thank you.