A Note From Your Doctor

I sympathize with your plight, you are 'between a rock and a hard place,' as the expression goes. I understand that you do not want to reveal the exact nature of the condition that you are working hard to correct, but you are in a 'rocky' phase of that treatment, and it is manifesting in your work performance. Whether or not you are being forthcoming, your supervisor will be venturing guesses, and she may even have arrived at an accurate conclusion. What she doesn't realize is that your drop in performance is due to a treatment process, not as a result of using alcohol on the job! I would suggest that you see your medical doctor, who really should be aware of your secret life anyway. If you have been attending a 12-Step Program, you should be able to come away with a 30 day chip, if your physician needs some kind of proof that you've been attending meetings, but regardless, ask him/her for a note that you are undergoing a period of treatment. 

You have to be open about this to your physician, because [s]he needs to be part of the treatment process to ethically write such a note. It does not have to be specific, no doubt your supervisor will figure it out herself, but it presents a picture of you being in control rather than intentionally acting in some irresponsible way, and trying to deceive people at work. This is the best compromise I can come up with. Consider the bringing of your physician into the loop to be a fulfillment of Step #5: "Admitted to God, to ourselves, and to another human being the exact nature of our wrongs." If you do not have a regular physician, or the answer is 'no,' consider seeing a psychotherapist who has experience with substance abuse issues, to help you through this phase, but first ask if in the course of therapy, [s]he would be able to supply you with such a letter. If you were my client, and you were earnest about getting clean, I would write such a letter. 

Your secretiveness is a form of deception that you need to forego anyway. You already are seeing the writing on the wall with regard to your job. It may be something of a gamble to bring your supervisor into your personal life, but if you do not take a chance on her ability to understand, in her current view, she is suspicious of what's up with you. Continued paranoia of your supervisor may well result in your termination. Best wishes!