when your scanner hates its owner

I can't find the way to calibrate my scanner and change it back as it was. it used to NEVER give me full whites, but I could easily fix it. now it gives me the brightest colors and KILLS all the shading passages from *any color* to white. so here is a bad scan of one of the drawings I'm making for shool

watercolors, coloured pencils, gouache, chalks. mainly watercolors!