There is a pimple on my stomach that changes every single day, what is it?

Good question.: And it is one for your doctor. This needs to be seen if you are to find out what it is. You mention it changes, and that is potentially worrisome, although it may turn out to be something common and benign, call your doctor and describe what's happening. I am sure you will be asked to come in for an office visit shortly. Good luck!

Unlikely a pimple: The skin that forms pimples does not extend to your belly.However, there are hair follicles there that can become infected by skin germs & look similar. It can also be a deep abscess, an early skin cancer, a wound from an unrecognized event, etc. It may be worth the effort to have it examined, since there is no way we could say it is not a worrisome problem.