My week old baby has been sleeping so much the last two days, and not eating as much per feeding. He hasn't been fussy but grunting a lot. Pooping n urinating just fine too. Is he ok? What's wrong?

Depends. Not sure what you mean by grunting but that word bothers me a bit. The sleep, eating and pooping sounds ok. Does his breathing sound ok? If concerned i would not hesitate to take your baby to the pediatrician . Grunting is not a normal baby sound but it might be just your description for a normal sound.