I would disclose the information to your boss. It's a matter of fact! But at the same time, I would let your boss know what you intend on doing about it.......like see a doctor......If you'd like to talk about sleep disorders mail me............I'm very familar with reasons why one doesn't sleep.......
I have a friend who had the same symptoms, and he was diagnosed with Sleep Apnia, a very unpleasant condition. I think your employer should know your problem.
Issues with sleeping.. alot of us have hem.. I go through days on 3-5 hour sleep. If your boss is understanding yes.. if hes a real dandy of a dictator.. no.. then your giving him more of a reason to shoot you in the foot and try to get rid of you. Though all you really need to disclose is your having medical issues.. and its affecting your sleep.
No, just call in sick. Your employer does NOT need to know details.