It seems to me that your problem is with the Highlighting Colour rather than the Brown colourant. The Highlighting Kit may well contain a bleaching product and several uses with a product like this can cause damage if used incorrectly, and overlapped over previous highlights. If the lights in your hair are damaged it will make all your hair feel dry and brittle. Please do not panic, you will not wake up bald!!! ...More >
Your first course of action is to repair the damage and begin a treatment regime. I also suggest that you do cut off some of the length and reshape your cut. The best and most successful treatment you can buy is called Colour IQ, by Goldwell. You can buy this from any Goldwell Salon. You need to buy the Blue-coded range of Shampoo, Warm Brown Conditioner and the Treatment Masque. I suggest strongly that you use both the conditioner and masque together each time you shampoo your hair. You will see instant results as it reconstructs the hair. Do this for the next 2 months, then after that use the masque every week.
I personally do not agree with Highlighting Kits for home use as I see 100s of disasters of this kind. It takes years of training as a professional colourist to be proficient and accurate with using bleaching products. So home use is bound to go wrong!