Are you taking iron supplements? If you are, I'd stop and talk to your ob about something gentler. I had constipation fairly frequently with my DD, but this time around I'm on a much lighter supplement, feel better and have had no constipation at all. If your stools have been darker lately, the excess iron could be contributing to your problems.

Lots of fruit and vegies are also good. Your bowels do change/slow down, but shouldn't be by this much. Hope you feel better soon!