Hello,
If you have not started with your period then it can be due to primary amenorrhea but if you have missed your periods, then it can be due to delayed periods.
If you are sexually active then the possibility of pregnancy needs to be ruled out. Please do urine for pregnancy test and also get an ultrasound done for ruling out pregnancy. In case, it’s negative, then other causes of delayed periods need to be looked into.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
Have you ever had a period? What did your doctor say?