Well, if you really want to go back to sleep, I recommend praying and reading Scripture (or reciting memorized Scripture if you need to keep the lights off). Other strategies I use include getting up, walking around a little bit, and going back to bed.
Also, “So much on my mind” and “I can’t think!” are two contradictory sentences. Philippians 4:6-7 is what I’d look at for God’s amazing peace, and Psalm 4:8 is a comforting Scripture to help calm down at bedtime.