Have you considered just changing the current character? There must have been something you found interesting in order for you to choose him in the first place. Could you maybe focus on that and stop doing the other things that you've found you don't like? Perhaps an alignment change, or some new oaths (ie. "I'm am a holy warrior, not a healer." so no more healing). Or heck, forsake your god altogether and maybe the DM will let you trade in cleric levels for fighter levels.
Anyway, for the sake of continuity, you should at least think about salvaging your current character before you just write him out of the story. But if you do need to ditch him, you should at least play him out until a time comes up to swap in someone new. And if the character is leaving, maybe the DM can do something interesting with him (ie., he's been a traitor all along and now he has chosen to strike). Just some thoughts...