Mirena birth control !?

okay, so i am 15, going to be 16 in december. i have been taking aviane (a pill birth control) since novemeber of 2010. recently i have been throwing up alot and my mom thinks it from my pill so im going to the gynecologist soon and im thinking of different birth controls. well mirena came to my mind. it works for 5 years and i wont have to take a pill everyday. i am sexually active so i want something that works. my question is, why is it better for people who have already had a child? would it still work for me? & will it hurt to have sex with it in? any help would be great. thank you.