Why are you not allowed to take medication? In general I have found that psychologists like to stay up to date on what meds you are on in order to give you the best care. Sometimes they see you more frequently then you see Pdoc so they can be on the lookout for potential issues resulting from the medication. They don't have the expertise that your Pdoc will have but they typically have general knowledge of psych meds from experience. For example, if you were given a drug to treat a symptom and all of the sudden started being really zoned out and exhausted, the Psychologist may think about the possibility of it being med related which he wouldn't be able to point out if he didn't know.
Therapists and Psychologists generally do not communicate with each other without your explicit consent. This has exceptions of course but this is the general rule. If you have concerns about the two talking about you (you don't even have to mention why), I would suggest politely asking your Therapist to ask before communicating with your Pdoc.