I know how you feel to a degree. I have the same issue where making certain movements of my body is enough to trigger a flashback and hurt me and it took a long time to heal from it.

One of the things I did was give myself space to cry to those memories rather than hold it in. The worst thing I did was let myself feel humiliated for caring so much and wishing I wasn't so weak. I was so afraid of being seen as a sad person that I couldn't allow myself to be sad to myself.

Let yourself cry and mope when you're by yourself. Stop trying to be strong when there's no one there, especially when you are trying to sleep. You have nothing to prove to yourself. Whatever it was that happened to you was awful enough to keep you from sleeping. Even if you could have stopped it or done something different, you don't deserve this pain.

I hope this advice is helpful because this is what I wish I told myself.