If a endoscopy and flexable colonoscopy come back clear what could this severe abdo pain be help please?

Maybe something else. Lots of other organs in the abdomen and pelvis. Other tests that may help include:careful history and physical exam, labs, sono of abdomen/pelvis (safe, painless, no xray), small bowel evaluation with capsule study, ct or mr enterography. Sometimes can be from adhesions from old surgery or inflammation, sometimes internal hernias, sometimes referred pain from back. Keep looking.
Options. Blood tests, ultrasound, ct scans would all be options that you could discuss with your doctor. Sometimes a diagnostic laparoscopy is a last resort.
Only see inside. Scopes only see the inside of the colon and stomach and a small portion of the small intestine. If your problem is not in these places, or possibly impinging on these places, then it will not be seen. Gallstones for example. Or pancreatitis. Or a ruptured ovarian cyst. Or even an appendicitis would not commonly be seen on scope. So more studies may be needed as well as a good exam, history.