What Causes Muffled Ear Along With Stinging Sensation While Burping?

my left ear feels stuffed/muffled and pings when I burp its been on and off for almost 3 weeks its happened before and it goes away for 3-4 months then it comes back its been happening for a yr now my doctor says its my sinuses fluid behind the ear drum and recommended Claritin D im about to change insurance again so I wont be going back to him but id like to know if theres anything I can do or whats causing this at times it can mess with my balance