It sounds like you're trying too hard. Power is a two way deal. It has to be given as much as taken. She want's to be your slave. Let her work for it. It doesn't sound like you're enjoying this like you should. Obviously you're doing it wrong so you need to change your strategy. I think it's better if you sit down and think through what you want and what you take pleasure in, and train her to do that for you. I'm certain she'd enjoy that if she's as submissive as you say. If she doesn't...well.... I guess the two of you might take up knitting or something else less D/s.

Priority number one is to tell her the same thing as you wrote here. Tell her you have this problem. She won't think less of you for showing yourself weak. That's part of being human, and I'm sure she'll understand. Trying to live up to an image you're not, (ie flawless Master) will never work for anybody.