My wife is finally pregnant after 2 years of trying, but she's unhappy?

Me wife and I are 29 and 31, and we've been trying to have a baby for the past two years. She's had 2 miscarriages during that duration of time, but now she's pretty much in the clear as she is 6 months pregnant. She was happy when we first found out, but her happiness has severly declined in the past months. She doesn't want to do any baby shopping, talk to anyone about this pregnancy, dicuss the baby, etc. She doesn't even like me at the ultrasounds with her and she has become very distant. I've tried asking her about this, but she says everything is fine. Have any other women had this problem? Is there a way I can help my wife? I am very happy about this baby but it's difficult because she isn't.