What foods/vitamins improve hair growth/stop hair loss?

For the last 2 months or so my hair is falling. Every day, when I just randomly run my fingers through it, I have almost a full handful of hair that remains only in my hand. I never had this problem before, I do not dye my hair, I do not use any product harmful to the hair and the like, then I can not understand what can cause this. I also changed my shampoo and conditioner and gel stopped using only case, but that did not help with hair loss. I think a fairly balanced diet, do not take any medicine, so I’m almost at a loss to explain why my hair keeps falling out. I do not take vitamins, but I am considering starting to take some in the hope of stopping hair loss and generate new hair growth. I’m relatively young – in my early 20’s, so I know it’s nothing given age. Although I had some stressors for the past few months, but I’m not sure if stress can cause such a significant loss of hair. I would really appreciate any advice regarding this.