Hello Sir William. First at all i have to say that you did wrong ! After a sinus surgery FESS the follow up is very important. Anyway, you should go now, something is going wrong with your sinusis because you have some kind of infection this is why your mucus stinks and you still have headache. What is going wrong, you are wondering! After FESS the mucosa of the nose need some time to heal and during this time you should see your doctor , some times the sinusis can be closed again, specially the frontal sinusis. So, with less words, YOU SHOULD HAVE AN APPOINTMENT WITH YOUR DOCTOR, again. !