Help please! My left ear always pops and then sounds muffled/clogged

For a couple years my left ear has popped every single time i swallow, when i move my neck or jaw and when i talk, and the only way to get this sound to go away is if i sniffle really hard or hold my nose and mouth shut and suck in.  This will only help until i swallow or move my neck or jaw.  I am constantly sniffling and holding my nose and mouth shut which gets really annoying and no one wants to be around someone doing this constantly.  This has really been annoying for me and i've tried just about everything.  I hardly have a stuffy nose or allergies so i dont think its that.  I see people saying how you can hold your nose and mouth shut and blow out but this only makes the problem worse for me and pops both of my ears and they both sound muffled. Every time i take take a drink of something both of my ears pop and sound muffled which really discourages me from taking a drink of something.  Im pretty sure it's my Eustachian tubes but is their anyway to prevent it from popping and/or sounding muffled?   I'm going to see a new doctor about this soon since my previous doctor said it would pass as i get older but it has been years and I'm afraid they won't be able to solve this annoyance!  Please someone give me some input I really dont want to live like this for the rest of my life... please help!