Get rid of the quiver if you shoot with it on. Then practice using the level. Like make it a point to level the bow, maybe not even shooting the arrow. Draw, level, aim, let down. Over and over again till you get it right.

You say you can't stop from canting the bow. There is no such thing as can't. There is only the lack of will and discipling your mind to tell your body what to do. Don't think about NOT canting the bow. Think about what you want to do right.