Nutrtional deficienc. Some times lack of certain minerals/ vitamin can give peculiar tastes in mouth. Also chronic sinusitis can also change taste buds.
Multiple reasons. There are multiple reasons you may have a bad taste in your mouth. The most common causes for bad taste in your mouth is medications, oral health problems, systemic diseases and environmental chemicals. See your dentist or doctor for further investigation.
See a dentist. To rule out decay or gum disease.