BC and Plan B

So a couple weeks ago, me and my boyfriend had sex. I was on top when he came, and when I got off, the condom was broken. I just recently started taking birth control, and at the time I was about 6 days into the first week of the pack. I started freaking out so we immediately went to the nearest Walgreens and he bought me a Plan B pill. I took it instantly. I have had sore boobs, I’ve threw up once, and my mood is all over the place. I know that the birth control would’ve protected me, but I’ve read that it isn’t completely effective until you’ve took the first 7 pills. My period is due in 4 days and I am so scared. Is there a chance I will be pregnant and was it a mistake to take Plan B even though I was on birth control?