I can imagine this is very frustrating for you. It is something he is going to have to learn if he is to continue with you.
I think sometimes men get into a mode of thinking to themselves, and it is an interruption, and an extra effort to try to stop and talk about it. I do this sometimes. I'd like to say that I've learned when to open up to my wife about it, but that's not entirely true. I'm much better than I used to be, and I recognize that it is a real need for me to stop and talk to her sometimes, but there are still times when I find myself thinking, and talking about what I'm thinking about is difficult either because I'm thinking faster than I can talk, or else, it's just too much effort to talk ... that last one is actually true sometimes - sometimes I think, and just don't want to spend the effort to talk.
I would think just out of courtesy he should not talk up a waitress in front of you, especially if he recognizes that you are sensitive about your appearance right now. I know when my wife was pregnant, she was as attractive in my eyes as she ever was - I recognized what was under construction there and I thought it was a beautiful thing. However; every guy is different. I'd ask if you told him that it hurt your feelings when he said that, and expressed your need to be built up and have his involvement. Certainly, I don't think going upstairs and crying while he sits downstairs unaware would be helpful. He is going to have to know what is going on in your mind and heart so he can respond. He may not know how to respond, so you may have to help him understand how to respond in order to get him started in the right direction.
I'm not making light of what you're saying, but your latest post really reminded me of something humorous I saw a while back. I'll post it here, but I'm absolutely not making light of your feelings. I post it because I've found it to parallel what's happened with my wife and me a few times, and it is rather funny if you think about it. I've had to learn to open up better, and she's had to learn that sometimes, I just don't do that well at opening up while my mind is busy.
One thing that really helps me to talk is if I walk. For whatever reason, when I'm sitting, my mind tends to be so busy that I can't really talk. In these times, if my wife takes me out for a walk, I find it much easier to listen to her, and much easier to talk to her. If you can go for a walk, or find some other activity that the two of you can do together that makes his hands/feet busy, it may be that he can find it easier to talk as well - just a thought.