Hve been caught up with cold for last 3 months. Had consult with a doctor also, according to them its a temporary sinusitis. What should I do please adv?

Sinusitis. This inflammatory condition can become chronic, particularly if mismanaged during acute stages. See an ENT doctor and have yourself evaluated appropriately by an expert. Hope you are better soon.
Strangely enough. This might be too much sugar in your diet. It is easy enough to find out simply by stopping sugar.