Is it possible to be congested and have post nasal drip? what is the best medication?

Yes: If you have an allergic problem with your nose, sneezing, nasal congestion, runny nose, itchy nose, and post-nasal drips can occur in various combinations of the above. It appears that you have asthma as well (on Dulera). Try a nasal steroid to see if it helps. If not consider seeing an allergist who will likely be able to chart a better treatment course for your nasal and lung problems.