Slowed down sex life

Since i got married me and my husband were having sex usually every day or every 2 days this lasted a year then i got pregnant now im 28 weeks and we go 3/4 days without having sex and im just confused does this mean our sex life is boring or hes just not as interested in me because im pregnant.. i havent gained much weight maybe about 4kg and no huge belly yet he never used to turn me down but now days i get a flat out no im tired or i have work in the morning and thats a massive hit to my confidence because its not what i had gotten used to can anyone offer me some advice? What can i do to fix it or is there rly nothing to fix? is this just normal and im working myself up and having unrealistic expectations? I never have had previous sexual relationships i lost my virginity to him when i got married