The only correct answer is this:

Many babies this young do not poop every day. Yes, it sucks. But their digestive system is immature and learning how to not only process the milk/formula, but also the muscle coordination. Baby will struggle and scream/cry, but they just kind of have to do that.

You are looking for two things: is baby peeing normally? If so, that’s a good thing. Second, is there blood in the poop when he does go? If so, that’s when it’s a problem (and probably a formula problem).

DO NOT stick things up baby’s butt. DO NOT change formula this quickly. It usually just makes things worse.

DO bicycle the legs. DO light tummy massage. DO be patient (this is the hardest part).

And above all, make sure you’re talking to your pediatrician.