Congrats on your time alcohol free! That's awesome.
Some obvious suggestions: No caffeine after noon, not even chocolate. Exercise. A late night calming routine.
I also second Melatonin. (it's a natural substance). Has really helped me.
Do you find that your mind is racing? Are you a worrier? I used alcohol in a self medicating way for anxiety and depression. When I stopped I had a terrible time falling asleep, because I used to just "pass out". But it has evened out, and I am able to fall asleep naturally.
Have you talked to your doctor about it?
Best wishes to you and congratulations again!