I'm wondering how I can find out if a certain vitamin or herb will decrease the effectiveness of my birth control pill.

I am currently dealing w/ hormonal adullt acne and am taking a BC pill to help this along w/ zinc, b-complex and C.

I have read that omega-3 and saw pallmeto are good in treating hormonal acne, but if used for these purposes--or any other--wouldnt it effect the BC pill if it is effecting my hormones? I do not want to end up pregnant!