Does anyone have any other advise on this? I NEED to be able to scuba dive.
Bongo, I don't want to repeat things your ENT may have told you, but it is important to understand what you're trying to do when you equalize your ears. I know this sounds overly simplistic, but what happens when you descend through the water column is the pressure builds on the outside of your eardrum pushing in. The only means you have to counteract that, is to increase the pressure on the other side of your eardrum by forcing air up your Eustachian Tube to equalize the pressure on both sides of your eardrum. So your Eustachian Tube HAS to be open, but its not. It's closed. If it was open, the pressure would have equalized without you having to do anything.
So how do you open up a closed Eustachian Tube? To answer that, you have to know why it is closed. You could have a physiological problem, but your ENT said you were OK. You could also have a medical condition (cold, allergies, etc.) to cause temporary congestion in the tube itself. I would caution you very strongly against using medicine or nose spray to treat this condition so you can dive for the very reason mention above. Reverse blocks can be minor discomfort or a very serious injury depending on a variety of factors. It's not worth getting injured over. Now, if you're like me and have seasonal allergies and take medicine about 10 months a year like I do, you have to make a judgment each day if it is safe to dive. This is where you have to be familiar with your medical condition and as you gain experience diving, you'll know those days when you have to say you can't dive. And those days do come.
Now let's talk about the most common reasons people in the water have closed Eustachian Tubes and what to do about them. One that is often overlooked is equipment issues. A hood or neckline of a wesuit can push in on that place in your neck where the Eustachian Tube goes up to the ear. Proper fitting gear is important here, or you can try pulling out on the hood/wetsuit so your neck is clear. But the most common reason is pressure (external or internal) in or on your neck causing the blockage. External pressure can be caused just by the increased pressure you are under by descending thru the water column. Internal pressure is caused by the flexing of muscles in your neck that naturally happen when swimming on odd positions we don't often face on land or when being in cold/cool water, or even from stress. Here is where the hold your nose and blowing thing comes in, but that is just one of many methods. Actually, that doesn't work very well for me either. You mentioned moving your jaw, that's another one. Pretending you're yawning is a good one. What I do is swallow, or more accurately flexing all the same muscles I use when I swallow. What you're trying to do in these last 3 methods is flex muscles in your neck to move your Eustachian Tube around and hopefully open it up for a brief time. That's all you need, the pressure will equalize by itself at that point, you don't have to blow air up there. Understanding what is actually happening, can make it easier to correctly perform one of these techniques.
As someone mentioned, going slow helps a lot. The reason is, if you've descended a lot thru the water column, the pressure differential can get pretty large, and that just squeezes off the Eustachian Tube even more making it harder to open up. Surely, if you started at the surface and snorkeled straight down to 7-8 feet, it would be a lot harder than if you had cleared your ears 3-4 times on the way down to that depth.
In most cases, if there is not a physiological reason for it, a good instructor or divemaster should be able to work with you and advise you on your technique to overcome this issue. But definitely talk to them about it beforehand and let them know you are expecting to have trouble. Honestly, half the time people tell me that, I watch them closely in the pool and they have no problems because they are thinking about 100 other things and they just do it without thinking about it. I don't want to say its 95% mental or anything, because it's a very real problem, but I do think its partly mental sometimes.
I would go ahead and give it a shot at least. You'll never know for sure if you don't try, and its a great hobby. Trust me, its better than you even think it is.
Good luck!