Sometimes it's stress, or too much sugar in the diet, or lack of fiber , or a lazy intestine, or lack of time, or dehydration .....so you can't go to the bathroom .
Try eating tamarind or drinking the tamarind juice . You can make the juice simply by boiling the tamarind till everything falls apart ( except the seeds, and the veins) . Let the juice cool or add ice! It's a perfect drink! Take this on an empty stomach.