I Had Gastric Bypass 9 Years Ago I've Always Took

I had gastric bypass 9 years ago I've always took a prenatal vitamin like they told me I've slacked off over the yeArs on other vitamins that was recommended but in th last year I've took a prenatal & 10,000 biotin & my hair Is still in terrible shape ,dry, can't run a brush hardly through it ! Do you think I'm missing some kind of vitamin or what can I do to it ?