I agree with the other posters and you should have a sleep study done.

on a more simple level: can you listen to a radio at work or headphones? I find that listening to talk radio keeps me thinking on a second level (I know that may sound a little odd) and keeps me awake. I used to listen to political talk radio but for the past couple years I've switched to the fluffy, gossipy talk radio. either one keeps me alert while I'm doing my desk work. good luck!