Hello, has anything changed recently?
Any new medication?
Have you had a head cold?
What about your sense of smell, is that still the same?
Any problems with dry mouth?
In the absence of any medication, or physical changes to the taste buds or sense of smell, then we can eliminate most common causes of abnormal taste. You may also want to check for any missing fillings or possible dental infection that may be affecting your taste.
However as you mention a headache then there is a possibility that this is a 'neurological deficit'. It may be migraine related, or it may be something completely different however this warrants a visit to your doctor for a neurological assessment.
If you have any fever, any visual disturbance, or the pain is severe when lying down then go to ER