I Have Asked My Wonderful Internist Re This Prob.: Only

I have asked my wonderful internist re this prob.: only recommendation "try Biotin".
I have had fingernails which split and break at the slightest touch for about 6 yrs. I have used Sally Hansen products, and taken Biotin (in varying doses-2per day fro a month; 4 perday for a month; zero for a month) to no avail.This is getting so bad that no matter the time of year (I live in NJ), I've gotoneor two nails down to the quick due to break/splitting.

Thank you!