I have asthma and allergies, and am a little congested. i think it's because of post nasal drip.the mucus is white and clumpy? is it post nasal drip?

Possibly: Postnasal drip is a possible symptom of allergic rhinitis ("allergies"), along with runny nose, sneeze, itchy/watery eyes, etc. Post nasal drip is drainage from your sinuses that goes down the back of your throat. A certain amount of postnasal drip is physiologic, meaning that everyone has it--excessive postnasal drip might be due to allergy or infection.

Could be...: Your symptoms may be due to post-nasal drip. If so, there are prescription nasal sprays that could be prescribed so see your doctor for diagnosis and treatment.