T.W.
I worked in Dentistry for 15 going on to become a dental hygienist. I would tell you to stop the peroxide rinsing. That is only to be done on a very short term basis. It is too hard on the gum tissue and over a long period of time with deteriorate the enamel on the teeth. If you are brusing and flossing regularly you don't need the peroxide. Now not going to the dentist is a big " NO, NO" but we all go through that for a number of different reason. If you go for regular cleanings (which really aren't bad) then you don't have to face the BIG appointments of deep cleanings and root canals and crowns and such. The dentist and their team are used to seeing patients with anxiety and concerns and are equipped to handle that and help you feel as relaxed as possible. Bite the bullet and go and have a check up and cleaning and xrays. It is likely nothing at all and then again it could be something that needs to be dealt with immediately. If you are having discoloration in that tooth and the gum is sore, it's likely the tooth that is dying and is in need of immediate treatment. But without seeing you and the tooth we can all only speculate.
Dr. Holloway on Del Prado just south of Hancock Bridge Parkway is very good and a really nice guy. I am sure you can get a ton of recommendations on here.
Good luck, you'll be fine and you'll feel a lot better after you get this taken care of.