If all tests are negative you may have a condition called chronic fatigue syndrome which develops in some people after a viral illness like infectious mononucleosis. This gradually resolves. Some studies have been conducted on the benefits of probiotic so you may try sporlac two tabs twice a day for eight weeks and see if that helps. If you don t have any medical problems that prevent you from exercises you may try graded aerobic exercises to improve your well being.I presume that your blood sugar levels and thyroid are normal. You may also get your hemoglobin checked if that has not been done because low hemoglobin called anemia may cause fatigue and lightheaded feeling. Since you mentioned uterine polyp, polyps may cause chronic blood loss which may cause anemia so hemoglobin test is essential. You may get the polyp removed as per your doctors advice etc. Regarding nausea and indigestion you may do a test called H.pylori breath test or Urea breath test . This is a simple test to detect H.pylori gastritis and if positive you may be treated for it as well. Best regards