Unfortnantly it is just the way some men are. Sometimes it takes the man going to the dr appointment and the dr telling the husband that no harm can come from having sex. For some that still doesnt work....
Some men dont like the changes that go on down there the further along you get, while others are just absolutly thrilled. If he is one of those types of men who are fairly set in his ways and likes things just the way they are typically have a little bit of a hard time adjusting to the changes our bodies undergo during this time. Just know that you are not alone and you may have to invest in some sexual toys until after the baby is born.
But try to talk to him and let him know how you feen and listen to how he feels and hopefully you two can works something out.
Best of luck!!!!!!!!!!!!!!!