When you are pregnant, the fetus creates a pull on your spine which can cause a lot of discomfort and pain. Try these exercises from John Elder, clinic director at the Egoscue Nashville clinic.
https://www.youtube.com/watch?feature=player_detailpage&v=NLuuaY1rVSY
Then contact Pain Free Santa Fe to find and correct your specific posture issues for a healthy pregnancy and a pain free life.