Hello,
If you have not had intercourse, then this delaying of periods can be due to conditions that affect the ovaries, uterus, hypothalamus, or pituitary gland. It could be hypothyroidism, post pill amennorhea , polycystic ovarian syndrome or less frequently a pituitary tumor causing high prolactin levels or a hypothalamic disease. Seek a gynaecologist immediately who will take a careful medical history ,a physical examination and investigations.
I hope it helps. 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 taken a pregnancy test? i think go and see a gyni to have a check up. you are due to go once a year if you are sexually active.