You are doing the right thing by no longer casting, but I'm not convinced of this whole "dark magic" thing. There isn't a huge coven of white witches and their adversaries, the dark witches. Stuff like that lives in movies and books. In reality, magick and energy stems from what you're feeling inside. If you think you're a "dark" witch, then the energy you're sending out is in fact dark because that's what you believe of yourself. Like attracts like. Focus on yourself for now. Focus on the good inside you, the positive things you have in your life, and try to appreciate the beauty and life this world has to offer.