Hello dr, i have missed my period, its about 26 days over. just took peg test y'day, its negative, some abdominal and lower back pain with white discha?

Ovarian cyst: You probably missed a period because you didn't ovulate. A cyst can develop in the ovary when it doesn't release an egg. It will often go away by itself and your period get back on track. Severe pain or continued abnormal period means you need a gyn check.

Home pregnancy test: should be accurate at this point. Reasons for missed /late periods: low body weight, obesity, marked weight gain or loss, over-exercise such as in endurance athletes, breast-feeding, stress, illness, eating disorders (bulimia or anorexia), travel, hormone irregularities, drug use, medications (i.e., birth control) or med problem (polycystic ovary syndrome or Asherman’s syndrome. #1 reason is preg