Dear Kim,
You didn't say whether any other dental work has ever been done near this tooth. The only reason I bring this up, is that before I got pregnant with my first son, I was in a horrific car accident. The damage was very severe to my mouth. I had several teeth that had to have root canals and veneers to cover the dark roots.
When I became pregnant about 5 years later, I noticed a "white-head" on my gum. I could actually (I know this is gross) mash it and get the infection out. Days later it would be right back.
When I was finally able to afford to see a dentist, he explained that it was an abcess, but because I had had a root canal earlier, I was unable to feel it. (They seem to kill the nerves to that particular tooth, and close proximity.)
I pray that this is your case.
Love,
Mandi