late period neg. test

Aapri 🦋

so i had sex on the 18th & 19th of january and my period was scheduled to come on, on the 31st but it never did, i got some bleeding (medium/light flow) a week before my period was scheduled. i also took a htp 3 days after that & it was negative, so now my period is 13 days late & i still got a negative.. any clues as to what’s going on???