3 days late and pregnancy tests have come back negative, could i be pregnant?

Unlikely: Home pregnancy tests are reliable, so as long as you are reading it correctly, it is unlikely you are pregnant. Sometimes menstrual cycle lengths can vary by a few days from month to month. If you still haven't gotten your period in another couple days, you might consider visiting your doctor to determine the cause.

Unsure: Retest in a week 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.

Could be: If you had sex since your last period, do the pregnancy test again in 3-4 days. Use first morning urine and follow the instructions for the test carefully. If you do not wish to be pregnant, use contraception all the time, every time. You may consider implanted contraceptive, or IUD. Practice safe sex. Get HPV vaccine,