You want to prove your obedience to me? Show me, that you are more than just the pathetic little thing between your legs?
You want to prove, that not sexual desire or your wishes are the motivation for your submission?

Then there is no problem in locking you up, is there?
Don't cry! It will only be temporarily and I will even consider letting you out once in a while... If I am pleased and you deserve it, of course!