I have been using afrin (oxymetazoline) for about 15 years. It stopped working as well two years ago. I weaned off it for 3 months and still could not breathe right.?

See an ENT. You have some obstruction that needs to be addressed. Two most common reasons are a deviated septum and or significant swelling (hypertrophy) of the inferior turbinates. Both can be easily addresses by a good surgeon.