Can i be pregnant and not know it? hpt are coming back negative. last period was dec 19th. and im 3 days late

It's unlikely, but: It can be normal for a woman's menstrual cycle to vary in length by a few days from month to month. It sounds like you have had multiple negative home pregnancy tests, which are usually accurate. Just to be sure, you might consider making an appointment with your ob/gyn if your period doesn't come in the next couple days.

Repeat HPT in sev : days with first morning void. Reasons for missed /late periods: low body weight, obesity, marked weight gain or loss, over-exercise such as in endurance athletes, breast-feeding, stress, illness, eating disorders (bulimia or anorexia), travel, hormone irregularities, drug use, medications (i.e., birth control) or med problem (polycystic ovary syndrome or Asherman’s syndrome. #1 reason is pregnancy