How Does Champix Help In Birth Control?

Hi I am curious to know is Champix has an effect of birth control pills?? I started champix 20 days ago and now found out yesterday that I am 3 maybe 4 weeks pregnant? This is a major concern of mine since I never missed either pill anyday, I'm very good with remember to take them and now I am expecting another baby when I have a 5 and a half month old already.