BF babies can go a week without pooping. As long as he's peeing he's ok

That's normal for breastfed babies. They don't poop as often as formula fed babies.

I know this might sound nasty but when I had my first son the nurse told me if this ever happens to take a wet wipe and wipe their butt with a little pressure. It will stimulate them to go. Like a mother animal does with her babies. Hope this helps