Insomnia - how to forget the past

I look forward to snuggling down in bed with a good book and eventually become dozy. As soon as I make my pillow comfy and turn out the light I am wide awake. My memory comes into action and replays all the things that I have done wrong or regret in my life. I am almost 70 and these memories go right back to when I was a teenager. I have 2 brothers - one bullied me and the other I don't even remember from my childhood. Lots of these flashbacks are from my previous marriage and my children growing up. I feel so guilty about so many things that I cannot change. I get so tired and stressed I end up taking sleeping pills for a few nights but when I stop taking them the insomnia comes back. Last night I eventually went to sleep about 5.30 am. I guess it feels worse at the moment when I can't meet up with friends and chat and laugh.