Pregnant on the pill

For my ladies who got pregnant on the pill.. when did you realize you were pregnant??? I am 21 days late.. took a pregnancy test 2 weeks after unprotected sex but it was negative.. should i re test? Should i be worried?

*started the pill in January btw after my period.. got my period in February.. missed it for March. I’m on my last week of pills so according to schedule I’m due for my period next week.