2x PT and its NEGATIVE!!

Ive taken contraceptive pills for about 7 and a half years.. I stopped last year august. Sept-dec i have a regular period and i am 28-30 days cycle. January 14 supposedly my 1st day of period but still no sign of menstruation or any blood stain.. I took a pregnancy test 2x and its a negative result. Ive just wondering why ive experienced heavy abdominal cramps.. And this is my 1st time to missed period in my entire life with a negative result. 😔