If the time it's been going on is measurable in weeks, then I really truly think you need to get it looked at by a doctor, perhaps even X-rayed. Obviously SOMEthing isn't right, and it's not going away of its own accord. Ignoring it may allow it to get worse or cause damage which could have otherwise been avoided.

I would have suggested possible R.S.I. (repetitive strain injury) but the symptoms don't sound like it - not that I'm a medical professional. But take some productive action, please! You never know -