Sometimes the easiest thing to do is just straight out tell her you want her to hold the key to your penis for the weekend. You can position it that you go in on friday, then she can take it off, and have sex with you on Sunday night; she'll know that you didn't masterbate. Don't go with the 'don't let me out no matter what I do" just suffer in silence. If she has it in her, she'll do it for the sexual curiosity, and for the fun of it. During the weekend, I am positive she'll notice the changes in you! This gives her a little time adjust to the idea, and feelings will start to stir in her; I'm sure.
If successful, after your sex on Sunday night, tell her how you thought about making love to her all weeknd long, and ask her if she wants to do it next weekend too. What woman could resist? If her response is positive, your in for a long haul. Pretty soon, you can feel much more comfortable discussing the finer sides of chastity, and move the lockup day to Thursday, then Wednesday. Soon, discussions over her having "completely control of your penis" will make their way in.
But small steps; little ones, and get through one weekend without asking to be unlocked.
If you can bare it, and take those small steps, a few months from now you'll want to be let out, and she'll say no, then put you to work on her..
M