You're pushing too hard. You should breathe through it, don't hold your breath. Look into getting a step for your feet. We're designed to squat, not sit, and getting your feet higher can get things to line up better internally

I just squat on the toilet seat straight up, if I'm at home. It helps, it really does, I swear by squatting

At work they had to put signs up to tell all the Indian workers who came to the UK not to do this as they were always breaking the loo seats! Better to get a step for your feet and get those angles better aligned.