Hi. Are you sure being pregnant doesn't have something to do with it? My husband was a little strange about sex while I was pregnant. Some men have weird reactions to it.
Hon, you both are very young and perhaps he is under a lot of pressure with a baby on the way and planning on marrying you..............these commitments are serious and can be stressful when you are young. In other words...........maybe the situation is just too overwhelming and he is withdrawing a bit.
I don't know too many young guys @ age 20 who are prepared for a wife and a baby.