I would not disclose. Often when people disclose having any mental illness it opens up the ability to use anything and everything against you to remove you from a class or work on a degree and a job. Yes the ADA is suppose to keep this from happening but in reality they don't go to bat for individual people. Anyone I have ever known that discloses seems to get fired for something lame a couple months later.. Like retuning from lunch 5 mins late. If someone wants to let some one go or in your case school they will find a way.

I would instead use the " poor sleeping" to explain why you did something wrong and hopefully save your place. Many people say a lot of things when they are running on empty.