How can I change my boyfriends ual requests?

My bf & I had a great life at first but it slowed down. The only time he tries to initiate now is during a time when there's no way I'll be interested. For instance he'll come up behind me when I'm on all fours cleaning up something nasty (like dog crap) on the floor or he'll come home from work all sweaty, go to the bathroom for 20 minutes, eat a bowl of nachos & then proposition me as he holds back a burp. Even if we do manage to get it started he always wants to go straight for the & I'm not even warmed up yet. I'm starting to feel like I reject him all the time but doesn't seem fun anymore. He used to smell nice & kiss me. Now he just kinda grunts and pokes me if he wants to do it. I've tried y lingerie, role playing & giving him a sexy bath but it's not working. How can make him understand that I love him but initiating sex when I'm doing a gross chore or only poking me is not sexy. I realize sex can't always be romantic but I need some advice. Help!