Hi,
There are a number of possible explanations to your problem.
One explanation could be some sort of sinus infection that is causing a strange taste in your mouth. This is a common phenomenon so think if you've had sinus troubles. Another possibility is that you are tasting tears that are being drained to the back of your throat. This is sounds strange but that's where tears go when you aren't crying. A third explanation could be that you aren't drinking enough. The saliva changes in accordance with the amount of fluid we drink. In this case just try to drink more.
There are other possibilities but you could go ask your doctor and get a thorough checkup.
Hope I helped.
