I think I have the record here for withdrawal related insomnia at 3 months. it just went on and on and on and work was always there when it was time to get going. As Dee said, somehow we mange to do it and eventually get tired enough to drop off. Sometimes just a little sleep is all it takes to feel a bit better but even that can be hard to find. I didn't find any of the "remedies" suggested by others here did me any good but obviously have helped others. A hot shower always helped me to at least relax.
the thing that helped me the most was trying to keep a good attitude. I was quitting for a damn good reason and if nothing else the insomnia was a great big billboard that told me I had not used. I could feel all the other parts of my life getting better and better and knew that eventually - and it seemed an eternity - I would sleep again.
Stay away from the x. That is a sure road to ruin everything.