Late period and plan B

I was supposed to start me period 7 days ago but I did not. Since I was not on it, I had sex (the first time in 6 months) and he told me he thought some might have slipped out of the condom and I took a plan be just Incase... I am on day 7 of my period being late, should I be worried. It has been 3 days since I took the plan B and I took it right after we had sex