Probably not pregnant right?

So, I decided to skip my period and take my pill packs back to back skipping the placebo week. I had unprotected sex on December 1st but then started spotting around December 8th which continued for about 9 days. I thought the spotting was due to me skipping my placebo week so I elected to just have a period this month so I took the placebo pills and didn't get a period.

I'm 3 days past my placebo week and I think this might I'll just be in my head but I've been feeling weirdly nauseous every morning when I wake up and yesterday I threw up. there has to be a very low chance that I'm pregnant as I'm on birth control and I take it every night at the same time maybe I could have missed a pill and not noticed? Does this mean there's a chance I'm pregnant?