Drew, I have a similar problem but not quite as bad as yours sounds.
Forget the OTC stuff. You may need something stronger. Maybe a doc could help. ?
Had this weekend before last, still have some post nasal drip. Sudafed works, but you have to get the real deal and not the substitute. i.e.pseudoephedrine and not phenylephrine which doesn’t work nearly as well. Of course, leave it to the drug addicts to take pseudoephedrine and produce Meth. So say bye-bye the only thing that works and substitute it with a chemically inferior product.
Look for the Sinus version of Sudafed it includes Tylenol so don’t take anything else that also contains Tylenol.
If it’s even available in my state, you have to take a slip up to the pharmacist and they log your purchase in a state database. They are looking for people trying to buy large quantities of pseudoephedrine.
Meth heads used to go from store to store and buy out their entire shelf of Sudafed, take it to a make shift lab and smash all the pills then extract the pseudoephedrine to make Methamphetamine.