Can Pregnancy Happen While On Birth Control Pills?

Hi, may I answer your health queries right now ? Please type your query here...i had my period october 8th to the 14th. i had unprotected sex october 16th and 21st. i am on birthcontrol but miss a few pills so i doubled up on my pills till i caught up. i then got my period november 4th to the 10th... do you think i could still be pregnant?