Why is it that everytime I'm on my period I get constipated... And feel the cramps all the way down to my butt? :/

Pelvic hyperalgesia. Pelvic congestion, hyperalgesia (increased sensitivity to the function of pelvic organs), & altered GI transit are common with menstrual periods in predisposed women. Best to get a clean bill of health from your gynecologist before seeking the help of a GI doctor but irritable bowel syndrome can present this way. Watch caffeine intake, add water-soluble fiber, stool softeners if needed, exercise.