Welcome to the online community @Tjj -I wanted to thank you for reaching out about what happened, it can take a lot of courage to talk about traumatic experiences.
I'm so sorry to hear you went through this, what happened was not okay and it does sound like sexual assault. It would be really confronting and confusing realising that what happened to you was sexual assault and I just wanted you to know that you're not alone and what happened to you was not your fault. You were a child and couldn't understand or consent to what was happening.
I just wanted to share the service 1800 Respect with you who offer support for people who've experienced sexual assault as well as this article about what to do if you've realised a past experience was sexual assault, if these are helpful at all.
Just a heads up I've made some edits to your post and added a spoiler tag in alignment with our Community Guidelines. We'll be sending you an email soon as well to check in so please keep an eye out for that
The community is here for you