If you cannot sleep, do not try to sleep. Your body is going to tell you to keep trying, but in my experience, you ultimately have a better time distracting yourself as much as possible. We are talking about serious withdrawal here; the kind where the Restless Legs are so bad that the idea of not moving is nightmarish. For this instance, you are typically just running down a clock right? How long until refill, money, relief. Often this just means a night or two at most.
I highly recommend listening to music while you pace around. Put on your most inspirational stuff and do some laps around your place unti your legs are tired. When you just can´t do that anymore, go put yourself in the shower with hot water. I would turn the shower on and just lay in my bathtub. The sensation of the hot water hitting your skin will give you some relief. You can spend however long you can in the shower until you no longer are experiencing relief from the water. Usually this is 30-45 minutes.
Get out of the shower, put on you headphones and go outside for a walk. The idea of being outside with many things to look at and occupy your mind while you walk will lessen the sensations. You don´t have to go fast, just keep a steady pace and keep looking forward. Lose yourself in your music. Listen to those songs you always listen to when you´re feeling bad.
Next, switch venues again and turn on some comedy. It´s best to keep it really light when you are withdrawing. You wanna know what I watched last time I was really sick? I turned on my old standby BasEketball. It was one of my favorite movies as a kid and I used to watch it on VHS with my brothers almost weekly. I get to laugh and also feel some of those good memories; the kind that sustain you when you´re feeling empty.
You will likely feel like continuing to pace. Get up and move around as you need to. Do not think about geting high. It is only going to derail your thought process. There is no value in imagining getting high right now. It only will create peaks and troughs of despair and deplete you of what little energy you have. Your methods might be different, you need to keep your mind occupied.
If you actually believe you will be able to get some sleep, you be the judge, go lie down and try but don´t drive yourself crazy. Time will go by much more slowly when it´s just you, the four walls and your sickness.
If we need to talk about medications we can do that to, I just felt this was more a psychological thing.