What Causes Drop In Blood Sugar Level After Bowel Resection Surgery?

I have had a bowel resection (small intestine) where they removed 3 inches of my intestine. I have started having problems going to the bathroom and my blood sugar drops (I am not diabetic). I get very, very hungry and I eat, but am unable to go to the bathroom. I was told not to use laxatives. How can I correct this issue? I use Miralax and fiber pills daily as told by my doctors.