Severe sunburn burning in back not shingles help please!?

I have had this severe burning sensation in my mid to lower right in my back. Its not shingles. It may start out mild but then its so bad even my clothing hurts to touch it. This has been going on for over a year. My dr says it could be back strain but for a whole year. Plus it doesn't matter if I am sitting, laying down or standing when it flares up it hurts beyond anything else I have ever had. I can only describe it as a severe sunburn but inside my back with no rash or bumps. I am also very worn out. Please any help would be appreciated.