My kitten won't use the bathroom!!

so I got this kitten yesterday idk the gender. it was abandon and I took it in. it seems relatively healthy but it won't pee or poop! I've fed it kitten formula from a bottle several times and I've tried stimulating it with a damp super soft warm cloth and nothing happened. it'll lay with me, drink from the bottle I'm holding, and lick me but won't let me stimulate it to pee/poop. it freaks out if I try and keep moving on it and when I've calmed it down and slowly started stimulating it, it just scoots away. am I doing something wrong??? am I worrying for no reason and this is normal?? do I need to take it to a vet? its going to get it's shots soon if that's important but this whole no pooping or peeing thing is driving me crazy