There are lots of other possibilities, but your description is pretty accurate for the gallstones I had long ago. Did it start after eating a fatty meal? My gallstone attacks were fiercely painful and there was absolutely nothing I could do to ease the pain, but it gradually subsided on its own after 2-3 days, only to re-appear the next time I ate anything with fat in it. I think this is worth visiting the doctor soon. Good luck!
Maybe appendicitis or gallbladder, even kidney stones?