Thanks for your query.Based on the facts that you have posted it appears that your son who is 28 years old has feeling of his Glans
being wet all the time.
There is secretion of mucus like fluid from glands located in glans This secretion helps in keeping the glans moist to protect it from irritation of cloths and temperature of external atmosphere.
All his problems are related to Anxiety
.Please take help of a qualified Psychiatrist
and to allay his anxiety.