Do what you need to do to get by. Like a PP suggested, do your best as a mom, but for the rest...they'll just have to deal. Just be up front with your friends and tell them that although you are happy for them, pregnancy talk is (understandably) difficult for you right now.
I'm not a late loss momma, but at 20 weeks I believe you are. The ladies on the Loss board are wonderful, I'd definitely suggest you check that board out.