Should I worry?

So I’ve been taking birth control for almost a year now and my cycle is a pretty average length of about 28 days. It usually lasts 4-5 days. In late December I missed a week of my birth control. In that time my boyfriend and I had sex twice, protected and non protected. When I started taking my pills again, I skipped a week so that my period for January would come on time. It did and now a week later I started spotting which never happens to me!!! Is it because I skipped a week and my period would have came this week? Or is it implantation bleeding? PS. My period is always a dark maroon or brown color like this.