You have missed somethings. There are a few couple of ways to check.
First look on your map in each area. Everyone that has a quest should be in blue. Go to each of them and check.
The other thing that you can do is check your badges. You get a badge for completing all the quest in the area, like Loremaster (completing all quests in Atheneum) or Krok Deliver (completing all quest in the Krokosphinx).
If you're only level 46, you probably skipped just about every side quest possible.
All you can do from here is go back and look for people/creatures who need things done (have a question mark or exclamation mark over their heads). Since the higher level world quests give more experience, start in Dragonspyre and work backwards to Mooshu, Marleybone, Krokotopia, and finally Wizard City until you get to the level you want.
Since simply farming enemies gives paltry experience, there's no way around it; you have to go running down every street in every area to look for these side quests. If you should start another wizard, it's highly advisable to do all of the side quests so that you don't run into this problem again.