It is really hard when you are in this situation because dicussing the sexual aspects of our relationships is often difficult at the best of times. Have you asked him specifically if there is an issue - maybe he feels if he told you the 'truth' (if there is an issues kwim?) that he would hurt your feelings. I can see where he is coming from too with saying he is too tired for sex, but can stay up late - I'm the same myself, I can stay up, but also be too tired for sex because I'm too tired emotionally to give myself to DH during sex (I can't just lay there kwim?) but I can sit and watch mindless TV.

It is normal for men to feel different things about their wives/partners etc during pg. Some men find it doesn't change the way they feel about sex, some are a bit confused and unsure if they may be hurting the baby/third person/etc and others are just completely turned off - all of these reactions are fine and perfectly normal and it isn't shallow for them to feel this way. They have issues about it and they need addressing. It was said that Elvis never had sex with Priscilla once she was pg and after she gave birth as he held the 'mother' figure in such reverence because of his own love for his mother, that he saw being a mother was completely different to a lover.

And I dont' care what anyone says, being pg and then having a baby changes the dynamic of your relationship too - we just have to learn how to adapt to and enjoy those changes for the better.