In addition to what everyone has already said, the biggest of these suggestions being equalize early and often (equalize while your sitting at the surface and then as soon as your head gets below water), here is my suggestion:
When I started diving, I was having trouble clearing my ears. I did a river dive where the max depth was 20' or so and was hurting. I also had trouble in the pool, but always managed to blow hard and get my ears to equalize (not suggested!). However, one day I started using a hood.
When I wear the hood and equalize early and often; I have no problem whatsoever. When I do not wear the hood, while still equalizing early and often, its normally not a very good situation. Try getting a $20 hood and wearing it every time you dive (even though it will get a little hot during surface intervals during the summer). I asked some of my friends at my LDS why the hood helps and they said its possibly because it keeps a lot of the weight and pressure off your ear and just allows a small layer of water on it. I do not know and no one could say for certain as none of us are scientists, however, I know it works for me and it has worked for a couple other people I have suggested it to.
Worth a try! Hope you get it figured out!
Caleb