I swallowed a plastic water bottle cap, i don't feel sick or anything but i'm worried i won't poop it out.

Swallow: Most likely the water bottle cap will be in your stools within few days. It is none digestable so it has to come if not then you will need to have a x-ray to find out where the FB is at.

Swallowed plastic: Foreign bodies swallowed are often dismissed as inconsequential. Most pass through, especially indigestible items. The major concern is that the size and shape of an object may lead to it lodging in the intestine and cause bowel obstruction---a medical emergency. And plastic does not image well on xrays. Passing the cap may be felt to signal passing, but straining stool can also be done.