Only medical doctors can make a diagnosis or prescribe medication. Sometimes family physicians do this, but usually it's psychiatrists. Psychiatrists are medical doctors who specialize in diagnosing and prescribing medication for mental illness. Their services are covered by OHIP, but, as with other specialists, it can take a long time to get in to see one.
If you have questions about diagnosis or medication, start by asking your family doctor. If you don't have a family doctor, doctors at the walk-in clinics around Kitchener, Waterloo, and Cambridge can also help. If you're a client of John's and you don't have a family physician, John can refer you to a family physician who specializes in mental health and works out of the same building.