Chronic abdominal pain similar to cramps, std's neg, not a uti. With daily discharge. What could it be?

Female trouble. Your chronic pain may be related to pelvic organ engorgement, or chronic irritable bowel syndrome. Are you sure it is not a UTI. Have you been tested. A you constipated? Are your BM's regular?
Many things! Abdominal pain like this needs evaluation by a primary care doctor or gynecologist. There are many possible causes including pelvic inflammatory disease, endometriosis, ectopic pregnancy, fibroids, etc. The diagnosis depends on your age, other health problems, risk factors, and associated symptoms. You may need imaging tests. It could be something easy to fix, so please see a doctor soon!