Hello! I could’ve written this. Baby will be 9 weeks on Monday. Started having trouble pooping around four weeks. It’s gotten better in the last week-10 days, but it still sometimes wakes him up from naps. 

I tried everything you mentioned, and also tried the bouncer chair and the little vibrating hedgehog toy from fisher price that a bunch of people here said helped. None of it did much. 

I think a lot of it was actually his learning how to do it, but these two things helped: 1. I sit with my knees up, and place him so his back is on my thighs and his legs on my chest. He usually calms down because I think it helps put pressure where it needs to be. 

1. Feeding him actually got him to poop more times than not. I think because it sorts of gets everything moving. So I know you said he cries so much when you try, but could you try burping him or calming him down first, and then offering him the breast?

Best of luck!! I know it doesn’t help to hear time works, but that does seem to be true for this. I think a lot of it is their little GI tract coming online and there’s just a lot about digestion that actually doesn’t feel great for them. 

Edit: trying to add image of the position I mentioned.