Just can't find it in me to leave

So a little background I've been with my bf for 5 years now and he's a drug addicted I've tried so hard to help him and nothing has worked, now I've been put threw mental abuse for the last 4 years and this past year it has turned physical I just feel like I deserve so much better but just can't leave I'm so use to being with him I just don't know what to do anymore he says terrible things to me like I'm a fat whore and he doesn't love me then the next day acts like it never happened tonight was a bad night I just felt the need to vent sorry for the long post