Best vitamins for hair growth?

Destinee • I`m 26 years old and live in Charleston, WV. I am engaged to an amazing man, and our wedding is 09/24/16!! ❤️❤️
My hair isn't growing like I want it to. It literally has maybe grown 2 inches in the past 6 months. I straighten it all the time (which I know isn't good for growing it, but I have to because of my hair type), but I need a good vitamin to help it grow...any suggestions?? And where can I get them? Thanks!! 😊