It’s not necessarily your fault @The-red-centaur if you didn’t know how to say no, or stop him from what he wanted to do, or didn’t know the harm it could cause you, or your judgement was impaired by past experiences or substance abuse ......
And even if he is unwell, which you would have to presume, he has a responsibility over his own actions, particularly if he was older and you were very young.
Part of coming to terms with it al, is understanding boundaries, and your therapist will help you work things out so you can begin to heal. The most important thing in the moment now is protecting you from further harm.
Practice deep breathing when you are feeling really anxious @The-red-centaur ....it can really help to calm down your whole system, including spiralling thoughts.
Sitting with you.