Im a big +one for the recommendations above to equalize on shore on the boat etc. You'll also want to equalize just before rolling in and be exhaling as you roll. I used to be like you but practiced and learned to equalize early and often (and not hard). Also used Sudafed and such for awhile too but rarely if ever need it now. I still equalize on a regular basis when not even near the water. As another poster said, get your eustacian tubes used to working for you. Im not talking about the valsalva either, more like you equalize your ears on a plane, yawn with mouth closed, push out your lower jaw, that sort of thing. You should be able to hear them open for you. You'll recognize it from being on the plane, yes?
And as a few others have said, I also recommend you spend some dive trips other places than Coz until you get on top of this. Then you'll be able to return and have a delightful time.
And as a few others have said, I also recommend you spend some dive trips other places than Coz until you get on top of this. Then you'll be able to return and have a delightful time.