Dark Sugar do you take iron supplements,? I ask because they will do this to you, Skimmed milk has a laxative effect on the human body. Nestle tried taking out a patent on it.
I don't but this does happen to me far too often I never have a whole week without some kind of poo related problem
http://www.livestrong.com/article/324579-can-exercise-cause-constipation/ Part of why magnesium is effective is that it helps draw water from the intestinal wall into the intestine where it can soften and lubricate stool. Drinking sufficient water is needed. Exercise usually helps. Sometimes exercise is known to make constipation worse, but this may be due to not drinking sufficient water to replace water that is lost during exercise. Diuretics such as caffeine can worsen constipation because they cause fluid loss through urination. Blood electrolytes such as sodium, magnesium, and potassium are expelled with the urine, magnesium being the one that aids in reducing constipation. Vigorous exercise while consuming high caffeine products, not drinking enough water, and not replacing lost electrolytes is a recipe for constipation.