frostyjohn,

BINGO!! I think you just confirmed the problem!

Clindamycin is an antibiotic that is often used for tooth/oral infections that are involved with the sinuses. The fact that this problem is chronic and this medication "eliminated" your symptoms while taking it indicate that at that time it was affective against the species of bacteria causing the infection. The fact that you didn't stay symptom free indicates that the culprit of the infection is still present. Meaning, there is something that needs to be physically removed. As an example..... if you have a deep splinter in your hand and only a piece of it is removed, the area of the splinter is going to keep festering until it is removed in it's entirety.

Have you decided about the endoscopy yet?

Bryanna