Health advice

I really need some advice, i have been dieting for a few months now. I eat alot of fruits and vegetables, protein, less carbs than usual,, and my hair is falling out like crazy. I brush it in the morning and my brush is full to the max and hair all over the floor and it looks and feels much thinner on my head. Am i lacking an important vitamin? What should I do? Would taking multivitamins help?

I would really appreciate some advice because i am getting married in two months and do not want to be bald!