It was helpful to me to learn that other people going through cancer treatment had trouble sleeping. My anti-nausea medication, Ativan, helped me when sleep was elusive, but you might need to ask the doctor for something specifically to help you with this.
Years ago my sister Marnie (www.marnie.com) mentioned that when she wakes in the night she says “Who do you want me to pray for, God?” I have had precious times praying through a list of friends as I lay awake in bed. Sometimes I will feel an intense burden to pray for one friend, and when that burden lifts, I fall right back asleep. Sweet! It is comforting to rejoice in the uninterrupted time to pray for whoever God brings to mind. It takes “I should be sleeping” and turns it into “what an amazing opportunity to be used by God to pray for others.”
During treatment, as I lay awake praying, I would frequently become aware of physical discomfort that was keeping me awake. I needed pain killer, or anti-nausea, or other medication that had been prescribed, but I hadn’t taken it when I should. In that case, I’d get up, take the medicine, lie back down and keep praying until sleep arrived. If you can’t think of who to pray for, then start thanking God for things. That’s fun too!