BIG Phobia

I have a phobia that I am going to have to face tomorrow morning. I have dental phobia and I am having a root canal tomorrow morning. I've had people asking me what happened in the past that caused me to have this dental phobia and I can't recall any specific event. I can remember growing up and having bad teeth so I had to have a lot of cavities filled. It may be hearing the sound of the drill when I was having the cavity fixed. It could have been the needle that was used to inject the novacaine, who really knows.
Since turning 18 I have avoided the dentist as much as possible. At first my excuse was that I had no dental insurance. Then when I got dental insurance I thought that I was okay so I didn't need to see the Dentist. Then about 5 years ago I made an appointment for a cleaning and then ended up having some cavities filled and a root canal done. Then I stopped going to the Dentist, and this was about the time that I started dating Steve.
I've been avoiding the Dentist still but now I can't procrastinate any longer. I have a tooth on my bottom left side of my mouth that is broken, sensitive to heat and cold and painful the chew food with. Then on the bottom right side I have a tooth that is also broken (but not as bad as the left side) and it has recently become sensitive to heat and cold (still not as bad as the left tooth) and painful to chew food with.
I made an appointment with a Dentist and went for the visit this past Monday. They did x-rays and checked my teeth and told me that both problem teeth need root canals done on them and that I should do them about 2 weeks apart. Then he asked if I wanted the cleaning done that day since they would be putting cold water and bursts of air during the cleaning on my teeth - which may hurt the two that need the work. I agreed to wait until after the root canals are completed so that the cleaning wont hurt. If the routine cleaning hurts then I may be more unlikely to return for the routine services that I need to do.
Wish me luck...I'll be nervous/scared/terrified/weepy/anxious/etc. tomorrow until the root canal is completed.