my hair wont grow...help:(

i have been growing my hair for about 9 years now...i swear on my child i am not lying....it never has passed my boobs..i trim it .25 to .5 inches each year(have done every 4 month as well)... and still it isnt long and beautiful:(...i been take prenatals and probiotics for about a year and maybe its grown an inch ...can anyone help im tired of extentions .. i have bought expensive shampoo and conditioner...tried only shampoo...lol even would cut my hair on a full moon..i been desperate ...i have straightened my hair for years and died since elementary...anyone have suggestions?