Bleeding

So I have been on birth control for over a year. I take it everyday and don’t have a period haven’t even bled in the slightest for over a year. I take it with no period because of health issues because of my period and ovulating. Well tonight I got home and I had brown/red blood had some on my pants. When I wiped it was light pink and then wiped and nothing. I did miss a pill or two a couple weeks ago. Not two nights in a row but did miss. What are the chances of pregnancy?