Curious, I find that when disturbing thoughts try to sneak into my head at night, a distraction helps me fall asleep. Classical music helps, I focus on every note and don't allow my mind to wander, or reading something inspiring or funny or a good whodunnit novel helps too.
You can overcome this, you are doing well distracting yourself with positive things during the day, night is harder but not if you have a plan.
It will get easier over time. It took a long time for things to get this bad, just keep working on positive healthy things and you will soon start feeling healthier and happier again. I promise.