Metallic taste

Sooo...

Its been three days now that ive had this nasty metallic taste in my mouth. I brush, floss, rince and it wont go away. Its making my coffee taste bad. Ive set up at appointment with my dentist because i cant take it anymore!! I know that im not pregnant.. well aunt flow should be here in eight days. But have you ladies experienced this before? You know, before starting your period? Oh and dis i mention that my nipples are so sensitive?