The "white stuff" could be what is called Thrush. This is a fungal infection that can occur on the tounge. It's formal name is Candida Albicans. Do you use a steriodal inhaler for asthma by any chance? If so, you must rinse out your tounge and throat each time.
If it is a fungus, a doctor can prescribe Diflucan in pill form that has to be taken for several weeks. You should rule out thrush. All the best.