Ball pythons just don't poo very often. And they are highly individual in how often they do go. Especially growing babies...they utilize so much of the prey that very little of it gets turned into waste material, and it can take a long time (sometimes several weeks) for enough of it to build up to expel.
They often poo at the same time they shed...but not always. You may get a nice stinky present with the shed, but don't be alarmed if you don't. Just keep feeding as normal and your snake will go whenever its ready to.
EDIT: Oops..missed a question! The shed cycle often causes them to lose their appetite, but not always. It won't hurt the snake to skip a feeding during the shed cycle if you don't want to risk wasting a prey item (or find yourself stuck with an uneaten live rodent, depending on how you feed). But it won't hurt to try and feed during the shed cycle either. You'll have to figure out what works for you and your snake.