I had this happen to me. I was 13.
Any person, man or woman, who behaves inappropriately towards someone who is vulnerable (by age or lack of experience) is an abuser. It does not matter that you were 13, or 19, or 26, 36 or any age until death, it is very reasonable to trust a qualified professional who has a duty of care. You are not guilty of ignorance, naivety, or stupidity. You are not responsible for his actions, which continued before and after what he did to you.
Being taken advantage of in this situation is not being weak or mindless. You have nothing to be ashamed of. The most powerful advantage the other person has is the element of surprise and your respect.
If it's okay to take advantage of trust and respect, then let's all go out and beat up grandma. Clearly, it's not okay.
I know this as an adult. I do not beat up grandmas. I think that makes me quite normal and reasonable.
Tonight, you've encountered some news which will take a little time to process. On the one hand: it's independent recognition that what he did was not alright. On the other hand, you recognise that what he did was not alright, without requiring independent validity.
But, actually what you did do was protect yourself very well - you went elsewhere. That as a professional should have concerned him but it didn't. You WERE clear in your message to him. He chose to ignore it.
You are fully in control of what you do now. You may well wish to contact the police. I believe you, and there will be lots of other women thinking: I did wonder...
If you do, it may well be the case that a further trial is order against him. On the other hand, you may feel that you've dealt with this and that he is now suffering his choices. Just one thing to remember: whatever you decide to do now is because you're absolutely have the power to make an informed, adult decision. I support you, whatever you decide. But, please remember you didn't do anything wrong.