Married sex life advice needed please!


So since having kids 3 years ago our sex life has reduced to about once a week and that seems to work but lately since being more pregnant (18 weeks) and feel tired after work and kids etc hubby hasn’t been helping out not that he ever did but I thought since I needed to look after myself he would help out so because he hasn’t I always make sure I’m asleep before he gets to bed so we don’t have sex because why should I give him what he wants if he ain’t helping me out? I try to make little hints but doesn’t work. Does that seem fair? But then what if it’s the sex that will make him want to help me more? So lost 😩 I could go this whole pregnancy without sex so it doesn’t bother me lol but he needs to learn you give a little you get a little. Advice please