Its been months, Why isnt my hair growing?!?

Well, My hair is maybe an inch below my shoulders, The last time i cut it was about 6 months ago and that was an inch. By seeing things online, I saw that they said something about it growing 3 in. in 6 months. but my case is, that my hair HAS NOT grow at all.. everyday i notice it. im treating my hair well, good diet, no heat damage, Do you think multi-vitamin pills could work/prenatal. or that ovation cell therapy i herd on the radio could help??????????