It sounds to me like your relationship has what is most essential: communication. I may be wrong but something as clear as "collar-on" "collar-off" seems amazingly inventive to me. I didn't see you write anywhere though whether your partner enjoys these play sessions? Are they as into it as you are? Maybe the thing that is "missing" is that you are more sadistic than you want to admit and your vanilla partner can't provide you with that? This doesn't mean you can't be together, but ANY relationship's only hope is complete honesty and communication, you need to be honest with yourself first, then honest with your partner.