Not wanting sex

I feel so bad. My husband just caught me about to masturbate and was like damn really? Cause I’m always saying i don’t want to have sex. And i don’t. I’m rarely ever horny being 21 weeks pregnant and actual sex doesn’t feel that good. I’m super uncomfortable. I feel bad because i don’t want to hurt him but sometimes it just easier to do me and get it over with if i have that urge. I feel sick to my stomach and super embarrassed