"I was diagnosed with .... (state when) ... mention the symptoms you experience .... how the symptoms affect your ability to attend classes and complete assignments. When you started therapy what meds you have and are taking. What steps you have and are planning to take to do better at school ... maybe offer to sign a release of information so they can talk to your therapist (I know the instructions say the decision will be made on the documents but I do not think it hurts to offer). Tell them you will be unable to continue in school without the aid.

Good luck.