I can relate, I find many dental procedures uncomfortable. It is good that you are planning ahead for how to make them more manageable.
I think your dentist and mine might be using different equipment for digital X-Rays? Is it a 2 cm square card on a rod that you hold with your teeth? You will need to identify what is triggering the gag reflex. If its the taste, you can ask them to wash it off or bring something with you that has a different taste. Same for smell. If its holding something in your mouth, you can practice at home with something the same size/shape. (I learned to swallow pills by practicing with M&Ms, yum!) Figure out what is causing the reaction.
Worry is the interest paid on trouble before it is due. If you can't change it, toss the through out each time it pops up. If you can do something, do it!
Thanks for posting!
IR