Missed period, Negative HPT

Hello! I am in need of advice. My husband and I decided to start trying to get pregnant this past late June so I quit the pill ASAP and was due for my period on July 19. My cycle is 27 days, always on time and never missed a period in my life, even on birth control I had my periods right on time when I know others can avoid periods using the pill.
I took my first hpt July 25 and it was negative so I thought it could still be too early. I began to feel small cramps/abdominal pains that I hadn't felt before hoping maybe it was time to take another test on Aug. 5 and it was negative again. I'm sad it's negative but still confused as to why I missed my first period ever.