late period, but on birth control?

so I've been on bc for a month, almost two months. according to eve, my period was supposed to start today but it hasn't. now, my periods usually show up earlier than what eve predicts. I just took the last active pill in my pack last night so now I'm on the sugar pills week. my husband and I have had unprotected sex several times lately and he even finished inside me a couple times. should I be worried that my period hasn't shown up yet?

edit** I take my pill at the exact same time every day and have been since I started in February. I've only ever been a few minutes late taking it once.