I've got thick coarse hair which is layered and quite short. I have had it tinted at the hairdressers several times, looks good at first but then my hair, after about a week, becomes very dry and brittle even using conditioner. I've left colouring about 14 weeks or so and have a pale blonde/auburn fine remnants which will disappear probably when I have it cut on Tuesday. I really don't want to be completely greyish. In the past I've tried a box of colour lasting 28 washes and that's also left my hair dry, brittle no shine. Any recommendations? I'd like something that lasts six to eight weeks each time please and hopefully will nourish my hair if possible.