What Are The Chances Of Pregnancy After Taking Plan B?

Hi, I m worried I might be pregnant. I had unprotected sex a week ago and my period ended a day or so before, so about a week ago also. I just got my period again which makes me worried, as I am not on birth control. I took the Plan B pill 2 days after having sex, which I know is late and its supposed to be used ASAP, but we had unprotected sex the next day too. I m just worried what my chances are, and when I can take a pregnancy test and not be worried about a false negative. To be clear (I really don t want to get visual) but to help paint a better picture, there was no semen inside my vagina, just somewhat around it.