I Have Been Taking Kariva Birth Control Pills For About

I have been taking Kariva birth control pills for about two years now. I take them at the same time everyday and have not missed any pills. My period always comes on Sunday morning, today is Sunday and I did not get my period. I have no symptoms of pregnancy, no stress (other than worrying about being pregnant at the moment!), I haven't had any weight loss or gain, and I walk/run on my treadmill regularly. I am 31 years old around 5'2" and around 117lbs. Should I be concerned about pregnancy? Why would I not get my period like I always do?