Birth control pills are used for several reasons.. first of all the most obvious reason is to help a woman to not become prego.. but it is not 100 %.. so always use another alternative with the pill....
You take them exactly as prescribed by the doctor who wrote the prescription for this medication. If the directions are not followed to-the-letter, the possibilities of becoming pregnant increase...
There is no way to know for sure. Over the counter diet pills are not regulated by the FDA, therefore, no interaction experiments are conducted on them.