it is common for exclusively BF bubs to go days and days without a poop... but if u think he seems uncomfortable, you could try moving his legs like he is riding a bike (while he is on his back) the next time he is straining or grunting.... also a warm bath.... also some massage oil and rub his belly CLOCKWISE - this can help digestion (do NOT rub anti clockwise)... i used to give my girl water with a teensy teensy teensy amount of suger (im talking maybe 5-10 granules) if she was really upset with constipation, but she was a lot older, it did work though.

hopefully some the bath and massage might help.