Is this common?

I’ve been on birth control for about 2 years. Recently i’ve started skipping my period. (Skipping placebo pills and starting the next pack). I had breakthrough bleeding the last time I did this for about 3 weeks, so I’m not doing it again. It’s been about a week since I stopped bleeding but now my boobs are really sore. I haven’t missed any pills and take them on time. could I be pregnant?