First of all, did you disclosed your medical condition to your employer during the hiring process? Or did you just recently diagnosed with it?
If you were diagnosed with any sickness prior joining the firm, then you may be considered being dishonest and subject to be terminated. (Some companies state this clearly in hiring process).

Fret not about your psychological evaluation, the result is usually confidential - the psychologist will not reveal your details to your employer. My gf used to intern in one of these centres, so that's how I know it. Ethical centres will not reveal personal data to your employer or 3rd party that can reveal your identity.

It is always the better if you can seek help from the specialist ASAP. =)