First of all, I applaud your efforts in reducing you animal product intake. I really think it’s one of the most positive things anyone can do for their own health, the health of the planet, and of course for the animals.
I can’t say I’ve had much of a problem with this myself, but I would think that like anything else maybe your body just needs time to adjust, and trying out different things to see what helps couldn’t hurt. Everyone’s body is so different it’s hard to say what might work for an individual. I definitely agree that more water could help. If you haven’t tried the Kashi GoLean cereal (not GoLean Crunch, too much sugar and high in calories) you might want to give it a try, it has 10 grams of fiber/cup. Plus 13 grams of protein as a bonus.

I also find the more raw vegetables I can get down in a day the better, I usually have one big green salad every day.
Certain kinds of exercise can also help. I think I remember you mentioning that you’ve done yoga before? There are yoga exercises that are supposed to help keep your digestive track active and healthy (also others that are good for your immune function, nervous system, etc. quite interesting IMO). Here’s a couple related articles on that:
http://www.womenfitness.net/digestionyoga.htm
http://www.wikihealth.com/Yoga_poses_for_indigestion
Good luck, hope that helps!