every time i go to my clan it never shows the leave button next to my name

Contact a clan squad from this list: http://forum.toribash.com/showgroups.php

They will be able to assist you.

Your clan is probably in a war right now, try to cancel it if it's in your power or ask your clan leader to cancel the war. And a clan war can't take over 1 week, so in a few days it should be finished and you should be able to leave it normally.

If that takes too long for you I'd do what smaguris said.