If you do decide to reload to an early saved game, I would suggest going straight to where the dragon is supposed to be... avoiding any fights, get there as fast as you can, just to see if it was a problem with that particular saved game session, or with your overall game in general. If that makes sense.
If he's not there in the reloaded game, then I can't think of anything else to try except what I said in my previous post.
