Mari,
I feel so sorry for you and can relate somewhat. If this was my husband, I would pounch him in the face and scream "wake up, fool". He thinks you used him to get preggo, well you could say that he used YOU to get a great mother for his kids, obviously he is very concerned about their wellfair. Tell him that he is acting selfish and like a big baby, just b/c he can't get any sex. Have you tried doing things other than intercourse. If you have and he is still not happy then tell him, tough luck. You now have a responsibilty to your unborn child and you. Ask him how he would feel if his ex-wife did something that led to one of his children not being born, how would he feel?
You could easily say that he didn't want a baby and used YOU for all the sex, was he lying when he said he wanted a baby too, and now a little bit of time off is neede, and he is crying. YOu should tell him that you are very disappointed w/ how selfish he is, and unappretiative considering all the sacrifises you have made and continue to make for HIS children. And I'm sure you love it and don't complain to him everyday of the last 6yrs (especially when he goes away for his trips). He should be ashamed of himself.
Perhaps next time he calls to ask about his children, you should say, your son did this, your daughter did this, AND your junior was making me sick all day long, etc (always include your unborn child in the conversation about his kids, afterall this is ALSO HIS child). How do your older children feel about the pregnancy, are they excited?? if yes, then focus on that and show him that his children have embraced the pregnancy. Enjoy yourself, let him be miserable, don't join in.
Remember that if you give in to doing something that you're not supposed to and end up losing the pregnancy, the resentment that you will feel towards him will seriously damage you relationship. So I would just ignore him and not really listen to his complaints, or even try to argue w/ him. He is behaving like a child and no amount of arguing or explaining will help. So do what I did, when he complains, just leave the room, change the topic. Find something that makes you happy. You know what works for you. For me, I would have a cow. Normally I'm very calm, pleasant and rational, but if my DH was giving me a hard time or not enough support, I would just go crazy and leave the house to go for icecream. I was quite unstable emotionally when I was preggo. You can't feed into his selfish behaviour, and by explaining, walking on eggshells, you are allowing him to continue. You have to cut it off. Afterall he needs you more than you realize. You will always get finanicial support from him, weather you're together or NOT. Who will look after his kids so lovingly if you're gone???
MY DH wanted kids ASAP when we met b/c he's over 40, but when I got preggo, he would never want to talk about the baby, go to classes, or dr.appoints. I was furious. When I was in a car accident when I was 8wks preggo, he didn't ask how are you, how is the baby, no, he was mad b/c I totaled the car, and had odasity to say, "oh, I hope now you're not going to complain that your neck is sore".

In the first 6mo, he didn't want to spend much time w/ the baby either. But...there is some light at the end of the tunnel. After DS got some personality, DH has been great, can't get enought of him. So there is hope, but until it happens you really have to take care of yourself and the baby. Men have issues, and pregnancies often reveal them, in my case I had to grow a back-bone, and learn how to demand NOT ask things of my DH. When my DH said that I only use him for financial support, I would tell him that if he continues I will leave him, still get his money and at least not have to put up w/ his BS.
Treat your DH like a child having a tantrum, what do you do, ignore it, otherwize it continues or gets worse.(When your kids were young, and wanted icecream before dinner, and you said NO, they may respond by saying,"if you loved me, you'd let me have it, etc, etc. You'd say, "i'm sorry you feel that way, but I do love you, and you still can't have icecream, as we're having dinner soon." This no doubt would be followed by cries, screams, accusations etc.You would never start screaming back at your child (try at least), b/c you know that wouldn't solve anything, right? Not much different from your DH's behavior now? So look at your DH right now as your 3rd, no, 4th BIG baby and TREAT him that way. If you're persistant adn consistant, eventually the behaviour should stop (at least that's what they promiss w/ kids tantrums, lol) I hope this helps