Yikes! I'm so sorry, that would be very unpleasant.
I made a conscious effort to eat a yogurt or drink "kefir" during my last pregnancy because I got constipated early on. Never underestimate the power of probiotics. If you are already getting plenty of fiber, you may need some probiotics in your tummy to help your tummy out.
I also did a teaspoon of metamucil in an 10 ounce glass of water for the first 2 - 3 days to... um... get things moving...
Both were based on my OB's recommendation. I hope everything gets better soon.