When does nausea and vomitting as a side effect of birth control stop happening?

i'm on day 11 and i still feel sick. i havent been to school since starting it. the birth control i'm taking is called "diane" it has 35 mcg ethinyl estradiol and 2mg cyproterone acetate. i dont want to switch because my sister took it for 6 months for her acne and she has the most beautiful clear skin now. help???