Sorry to hear this. Your boss sounds more like a good friend.
My wife was misdiagnosed with tennis elbow then bursitis of the shoulder. For 4 months we dealt with the pain, treatment co pays etc. Finally we said enough and got a third opinion who did a proper mri and found out she had 2 extremely herniated disks in her neck which were crushing her nerves causing the extreme pain and numbness in her arm and needed a double microdiscectomy plus fusion. If we had waited any longer, permanent damage would have occurred. When we confronted the original doctors with this all they said was, "Well, you could still have a little bursitis/tennis elbow as well." Could, still, have, a little. I swear to you these are the exact words the "Doctor" used. Guess he had to claim something in order to avoid a malpractice suit.