I would feel hurt as well, and in terms of a breach of confidentiality, I don't believe there are any legal bindings which prevent people in the workplace to share information, though it does feel un-ethical. You could potentially have a case in terms of harassment or unfair treatment due to mental health "prejudice", depending on the degree of behavior. I'm not a lawyer, but it might be beneficial to consult with one.

People often think that prejudice is a black/white, gay/straight issue, but it effects those with disorders. I've been lucky enough not to be too effected by this attitude, but people can be so ignorant and succumb to stereotypes, as you have experienced. I am really sorry that this happened, and I wish you the best.