Constant stomach pain that comes and goes, causing some nausea. changing bowel habits. sometimes feel nauseous. i'm 22. ?

Go see ur family doc: Your symptoms need to be evaluated by your family doctor to determine appropriate testing. In the meantime, consider simple over-the-counter measures while waiting no more than a few days for your appointment: calcium carbonate eg Tums or Rolaids, magnesium eg Mylanta, bismuth eg Pepto-Bismol, Axid/Pepcid/Zantac, or even Prilosec etc for heartburn. Or simethicone for gas. Need pregnancy test too.