This....
Your boss is not your Dr or someone handling medical treatment for you, so I don't believe HIPPA rules apply. With that being said, he shouldn't discuss your medical history, but if it does pertain to your job, or you feel that it does then maybe he had to. I don't know. you aren't giving us much to go on here, so it's hard to really understand where the problem is.
The facts remain, companies have better lawyers and more of them than you do.... the most you will get for something like this (assuming that you can prove that he did it) is a headache and just be out the costs of your lawyer, or maybe win that the comapny has to pay your legal fees (just remember lawyers that handle law suits, get most of your money)
Worst that you can get is if the company wins and they hold a grudge is they can come after you for a wrongful suit trial and try to get money from you.