a few ideas
I have a very unique experience, so I won't go into detail, but I will be happy to share if you want me to send a pm.
I use earplanes (at Long's, Walgreens, etc...) on ALL flights now and dispose of them after one use. It greatly helps the pressure on descent, and I cannot fly without them. Sometimes I know I can't fly with them, and I need to cancel altogether. I take Flonase, sudafed, Zyrtec, Astelin, and Afrin before each flight. So maybe, depending on how severe your symptoms are, you could consider some combination of what the others have recommended and a couple of these options.
As funny as this sounds, my ENT dr. recommended before an urgent trip that I take BART (train in SF under the bay) because of the pressure to see how I withstood that, and then to take the elevator up and down in the BofA building downtown to see if I could "blow" my ears clear before I got on a plane. Luckily, I could the time I needed to, but there have been other times where I could not, and I did not fly as it would have been terrible for me.
I truly understand how painful this is and I'm sorry you're having problems with it.