Very unlikely. If you take it exactly as instructed you have less than 1:100 chance per year of getting pregnant.
why would you want to get pregnant while being on the pill? i'm sorry but that sounds kind of dumb. if you want to get pregnant stop taking it. it is possible to get pregnant while on the pill, i know people this has happened to, but there are also more risks involved of birth defects if this happens.
yes i agree with megancannon, stop taking pills if you want to get pregnant.