Advice on Growing out my hair?

Well for the past 2 years I've been straigtening my hair none stop. So as you can guess split ends, damage ect. Also, my hair is like just barely longer than my sholders. And I was just wondering would I be better off with extensions (if so what type) or just not straighten and take vitamins and stuff? Also, I really wanted to grow my hair down to my midback if that's even possible in the next 3 months. Thanks (;