Hi Hanna,
I am sorry to hear about your problem. What you could do is to still have a full head of highlights, back to back slices, with bleach on the roots only (6%) to lift the colour slowly.
A bleach bath should then be applied to the mid-lengths and ends until the honey and caramel tones are removed. The bleach bath will need to be one scoop bleach, one part 6% and one part shampoo. A toner will then need to be applied all over using 8/81 Colour Touch 1.9%.
Also use a good intensive treatment on your hair to maintain condition, such as Philip Kingsley's Elasticizer along with his moisture balance shampoo and conditioner.