Late period?

So I had my son two months ago and at my 6 week checkup I started birth control again. Well I was supposed to get my period this week and didn't. During the whole time I was taking birth control I was spotting. Before my 6 week checkup we had an accident and I got plan B a few hours later. There has been times where we have sex with a condom, then a couple hours later he will just put it in and then put a condom on. Could this have caused me to get pregnant again?? I'm sorry if this seems like a stupid question, I'm just freaking out. I'm supposed to start my new pack of bc Sunday.. I took a test and it was negative but with my son I didn't get a positive until 15 days after my missed period. Is there a possibility that I might have gotten pregnant?