My lo is one month old n has to exert pressure while passing gas or pooping. At times this annoys him.is this normal?

Yes. My LO used to grunt and squirm while exerting pressure to expel gas/poop. She would sometimes breakout in a cry too. But Like what debolina said, their digestive system is still developing therefore they may experience discomfort. You could learn to do a tunmy massage to relief baby of discomfort!