Almost year around post nasal drip that reflects in alternating ear discomfort with external wet ears. Facial, chest and behind ear seborheic dermatit?

See your Family Doc. It sounds to me like you have several issues going on at same time. Post-nasal drip could be from allergies which could lead to ear discomfort b/c Eustachian tube dysfunction. OTC antihistamines can often help. Seborrheic dermatitis is a separate condition (http://www.mayoclinic.org/diseases-conditions/seborrheic-dermatitis/basics/definition/con-20031872) as are your wet ears: otorrhea? infection?
Needs evaluation. By an ENT and a dermatologist, or better off a qualified and experienced allergist/immunologist who can sum up your case, if you have access to one where you live. If you are in Cairo, Egypt, check Vezeeta.com.