Sharp pain in abdomen groin area and lower back. black stool frequent urination?

See a doctor: You should see a physician as soon as possible. Black stool, especially if you are taking a lot of ibuprofen, can represent a bleed in GI track, normally in your stomach. While the pain does not seem to fit that classically, you may have a bleed somewhere else. Any peptobismol use?-also causes black stool. Best recommendation without more info is to see a doctor for physical exam and workup.