Hi and welcome Steph. I've added a trigger warning to your post because of some of the content. It's nothing to worry about, it's just so others can avoid it if they feel it will be a trigger.

I'm not sure you will ever get the answers to "why?" I still haven't. I find the best thing to do is to learn how to deal with those memories and move past them, counselling can help a huge deal with that, it has me. It might be worth speaking to your gp and seeing if they can direct you to any services.