I am chiming in with a different response. Hope you don't mind!
I am more turned on while pregnant than any other time. And it is always a lot easier for me to O. I am actually on Pelvic Rest right (week 6) until my bleeding and hemorrhage resolve and it has KILLED me! It makes me want DH more than ever simply bc I can't have him. So, to get by I take care of his needs pretty often. I find some strange pleasure in getting him off (sorry I couldn't think of a better way to say it). And usually once or twice a week I have such vivid dreams that I O in my sleep but wake quickly bc it ends up causing cramps so severe I curl up and pray for them to subside. I did discuss this with my OB and they said obviously there is nothing I can do to prevent the dreams and just keep hydrated and come in if the cramps ever continue.
Anyway, I do recall in my first and second pregnancy not being into sex that much but I was very young. !5 with the first and 18 with the second so maybe that had something to do with it. ? I am 28 now.
I second DefineGrace though about the taking time to pamper yourself and make some time all about you. I have 5 little ones and my DH is a pretty big kid himself most the time so there have been plenty of times in the past when I did NOT want to be touched in any way. Fortunately hubby picked up on this with time and would either back off and wait til I was ready OR sometimes give me the most amazing full body massage and by the end I was willing for anything. I think all the stress/tension being pulled out made me realize I was into it after all.
And just plain not wanting to have sex throughout an entire pregnancy is not uncommon. I definitely have friends who went without. Their husbands never wanted another baby LOL bc they assumed it meant another 9 months of no boom boom. Maybe letting him know you feel this way, stressed and overworked, would help. He might surprise you and start serving you like a Queen. Men will go to amazing lengths ;)