There are three components to a sexual agreement. First, establish a weekly frequency. I really recommend no less than once a week. Once you have established a desired sexual frequency, the next thing to do is to decide how this frequency will be accomplished on a weekly basis. You can pick days, split the week into parts, or rotate days, or weeks back and forth.
If the intimacy anorexic rarely initiates sex, then the intimacy anorexic does all the initiating of sex for the first 60 days. If both of you are intimacy anorexics, then flip a coin on who does 100% of month one and who does 100% of month two. If you are both keeping your sexual word, then go to a mutual initiating system.