What will make my girl go poo?

My girl is about 5 months pregnant with our first and she says she is having nothing but bunny poo every couple of days and she is always complaining about her stomach being hard and achy and I don't know what to do to help her or what advice to give her. Anybody have any suggestions. She went to the store and got some Activia yogurt, some raisin bran, and some prunes, adn she has been drinking warm drinks tonight.