Hi,
I suggest you grow out the colour from the foils and in the meantime start using a pro-vitamin treatment enriched with protein to improve the condition and strength of your hair. Don't worry too much though because we shed different amounts of hair at different times and it may be that you're going through a period where the hair is renewing itself.
If the hair is breaking off though, in which case it won't be at the root, then this is damage that has possibly happened because of the colour change and in that instance you should go back to your hairdresser for advice. Usually a regime of careful treatments and conditioning is enough to restore any elasticity that has been lost.
Good luck!