I understand your struggle. Just try to drink a glass of water, after coffee, it helps, but obviously that's a way to avoid them. But if you already have those stains, and brushing your teeth doesn't help, you better ask for help from a dentist. He is a professional, and I am sure that he will give you good advice. And I will recommend you to solve this problem as soon as possible, otherwise you will have serious problems with your teeth, and you'll need dental implants. Hope my message will be useful for you.