Chances are your mention of being constipated is the issue here! Get you some laxative type relief from the drugstore, to get things going again. Couple ones I like are if waste is there and ready to come out, squirt two tubes of ointment from the small boxes of PediaLax or BabyLax in there, should come out in minutes. If not, take a Senocot (natural) pill, two days, and the stuff will move. Simple premix enemas are okay.
To overcome what is probably the lingering cause and left over from the stomach flu situation, get some "probiotics" in you from Acidophilus milk or Activia yogurt from the grocery store, two weeks of it will return intenstinal flora to normal and help break down waste. Then to keep digestion running smoothly, eat enough fiber foods, drink tons of water, and yes, exercise regular.
Some fiber foods include not only lots of vegies, but also stuff like oat cereal, whole wheat bread, salads. Lots of water means to shoot for about six glasses a day, enough to where you're not up all night peeing! And exercise, break a sweat three or four times a week with ANY activity that you like, you can change it up, you can go for walks or jogs around the neighborhood, biking, anything you can get into long-term and stick with it as almost a routine. I used to exercise most every morning after breakfast for practically my whole life.
Lastly, once you feel your bowels are moving along like they're supposed to again, you may need to put a little lubricant there after each shower, it'll prevent the chaffing that is sure to come from going a lot, since I think you're probably pretty clogged up, plus it often is interspaced by diarrhea, and a blue and white tube of PLAIN KY jelly from the drugstore works best, water soluble so it comes off each shower. If you happen to take vitamins every day, quit it, only take them once or twice a week, or some brands will clog you up. Get enough proteins to eat, chew them well.
Gosh, I hope you get to feeling better soon. You may feel a little oozy for a few days, but it will pass, and you'll feel hungry again, and it'll pass through you like it's supposed to.