Last period was 7/19. 28 day cycles never late. took hpt and blood test on 8/18 both neg. could i still be pregnant? or why would i be so late?

Anovulation: There are over a dozen common reasons to miss a period besides pregnancy. You have not given us any clue as to your life or situation on which to just guess about this. Most one month missed periods are just a missed ovulation cycle. But, extremes can cause this such as extreme dieting, exercise, stress, obesity. Hormone issues are also common.