the 'what if' thoughts are so common in grief. And as a child your brain wasn't fully developed to cope with such a shocking thing happening, and children often internalise things, thinking they were to blame - that they should have done x, or y. If you think about any children and when parents divorce they can often feel they are to blame, that they are not good enough or did something wrong. But it truly is not the childs fault, it's just the way their forming brain has tried to make sense of things happening.
I know I went through a lot of 'what ifs' - I should have been there, I should have done x, I should have chased earlier.
Exploring these thoughts can certainly help you- and many therapists are trained in techniques which will help. Don't be afraid to look around - find someone you get on with, understand what they are offering/how they can help you.
I think we can also be harsh on ourselves with our internal speak - when we stop and realise sometimes we find we are saying stuff to ourselves in our head that we would never dream of saying to a friend or anyone else, yet it feels ok to bash ourselves. I find it helps me to catch any of those thoughts, and remind myself to 'speak' to myself as I would a friend. If you knew a child who went through a similar experience now consider what you might say to them -perhaps if those words are kinder you can extend them to yourself. You were only little, you were certainly not to blame. When we get caught in the 'what if' game there is no end, we may add a what if, but cannot then account for what could have happened afterwards instead but the same ending would likely occur
As the nights have become worse, has there been some other stresses or changes in your life? Sometimes we can find that when other things are causing difficulties we can struggle more with older wounds/losses. So might be worth thinking is there any stresses you can identify which you can take some action to relieve? (such as, if work is stressful, can you get some support, or if you're worried about something are there supportive changes you can make?)
I hope talking with us here helps. If you haven't had the opportunity to talk about it, it can be hard to process how we feel xx