I have often found that patients who constantly feel mucus in their throat but have failed nasal-related medications (allergy meds, decongestants, nasal steroid sprays, etc) may be suffering from laryngopharyngeal reflux (aka, silent reflux). Perhaps this is what is troubling you. You may also benefit from an allergy work-up including foods. In the meantime, try eliminating dairy, caffeine, spicy foods, and wheat from your diet while you get an appointment with an otolaryngologist.

You are describing chronic sinusitis and needs an ENT evaluation.

Sometimes you just have to see the doctor to find out what is actually the problem. Your symptoms have a number of possible causes. Allergies, chronic sinus infection, acid reflux, abnormal structures or lesions of the pharyngeal (throat) mucus membranes, congenital abnormalities are some of the possibilities. I suggest at least one visit to your ENT doctor and have a real medical evaluation.

Most likely allergy but we do see vasomotor rhinitis occasionally in long patients

You need a full ENT evaluation, CT scan of Sinuses, Allergic testing so a diagnosis may be reached.

See ENT for evaluation and/or different regimen