sex during pregnancy

I am 28 weeks now, all of sudden my hubby stopped asking for sex, its like he lost interest. Malambing padin sya at inaalagaan ako pero pagdating sa sex, wala, hindi sya naghahanap since start of february, which is very unusual of him. I am getting worried and nabobother ako. Is this just a phase because im pregnant? may similar experience po ba kayo? i need help and nahihiya ako iask sya directly.