I am firstly so very sorry that you have had to experience something in your life so traumatic that it causes nightmares and effects you when you think of them and are alone at night, it must be so very frightening and I have no idea how this must feel but I am so very glad that you are here to get some support and some advice.
I totally agree with kiga283 in that talking does help so very much, and here you can remain anonymous and share as much or as little as you want to, to try to perhaps get some clarity around what happened to you and how to manage this situation. If you would prefer to talk to someone you can call Kids Helpline on 1800 55 1800, if you are under 25, they are so very wonderful and will also have some tools to help you through this.
I think that anything you can do now to address these issues stop them becoming bigger and stop them becoming something that really impacts your life or your future relationships. That talking and getting some resolve on these things sooner than later before they become harder to manage is a great idea.
You are so brave to reach out and ask for some help and I am so very glad you have, anything no matter how big or small you want to chat about we are here for you, not to judge just to support.
Huge hugs to you idkwhy