It sounds like your power button might be broken, or stuck.
If you by any chance had USB debugging enabled, you should be able to plug it into any PC and the phone will launch the recovery menu automatically. There should be an option here along the lines of "reboot phone" and that would get your phone started up.
The only issue I can see from there on is how would you put the screen to sleep after use?
Anyway, your best bet is to take it to your carrier and get their opinion.
Edit: I have heard of people cleaning sticky power buttons with toothpicks soaked in isopropyl alcohol. Just gently rub it around the perimeter of the button, then wait a few minutes for the alcohol to evaporate.