Hello! All the symptoms you have mentioned indicate a periodontal (gum) problem. The tooth has been asymptomatic for 5 years so there are less chances of a tooth infection. Swollen gums indicate gum infection along with the kind of pain you have explained. You mostly have developed periodontitis, localised if it's only that tooth with swollen gums around it or generalized if most of your teeth have swollen gums, not necessary pain in other teeth though!
Have you got a cap placed on the root canal treated tooth? If not then there could be a possibility of a fractured tooth.
Next Steps
You should visit a dentist & get a scaling (cleaning) done along with an x-ray (IOPA) of the particular tooth to rule out any infection / fracture or other causes for your discomfort.
Health Tips
Use a mouthwash as an adjunct to brushing. Get a scaling done at least once a year, if possible every 6-8 months. Please get caps for all your root canal treated teeth.