What Could Cause A Persistent Rotten Cheese Or Metal Taste In My Mouth For Over 3 Weeks?

I ve been having this rotten cheese/metal taste in my mouth for the past 3 1/2 weeks. It s not covid. I m not pregnant. At first it was only during certain food. Now it s progressed to more foods and I can t get the taste out of my mouth. I take care of my mouth so I m certain it s not anything oral. What do you think it is?