Was I abused or did I make a stupid choice?

I(m in my 20s) saw a video about the age gap (17-24) and the way it was portrayed in the film “call me by your name”.

Welp that video shook up some memories….
Haven’t seen the movie but this actually got me thinking about sth that happened when I was 15.

Let’s keep it simple, when I was 15 I went on a trip to Berlin, where we had an international project about European politics and queerness. One of the supervisors (I think 28), gave lil hints here and there looking at me some way. I didn’t really think about it at first, but then he made a comment about an age gap I fell directly into, that’s when I noticed.
Being a really horny teenager I did fantasize about it a bit, but didn’t really act on it (or I might have the next part is kinda blurry). I do remember tho that one evening he approached me in the bathroom/showers after I showered. He wanted to take a shower too and asked me to join him. I backed away and I wasn’t sure what to think.

The next part I can remember is me joining him, not sure how directly I ended up back with him. So it was just us in one of the stalls and he commented on my maturity (which for me was normal since I was an early bloomer and even grew a beard, even though I always shaved. I also did probably look somewhat older and was quite developed but he knew my age). I immediately felt sth. was off, but I couldn’t just get out of that situation and what happened, happened.

At this point I just need to add that I suffer from social anxiety when it comes to my wishes. I usually cannot really communicate them without getting really anxious, so that probably didn’t help and at that point it was way worse than now.

That’s not quite the “romantic” setting like in the film but it really reminded me there.

After the fact when I tried to speak about it with my closest friends (I did NOT have a stable home but that’s a different story), after weeks, they just told me I could just have said no. I could just have walked away and that it was my choice.

I accepted it as that, my choice, my wrong choice, because I was too stupid not to speak up. Then I couldn’t remember it for quite a while until someone mentioned Berlin and it came over me again.

And the fact that my heart is still pounding as I am writing this is probably a sign that it didn’t leave me unscathed. There were other worse side affects but that also might be a story for another time. I still feel like it’s my wrongdoing, but in the context of this video my heart races when I think about it.

Now I just want to know, was it my fault, or did someone use my immaturity and mental instability to exploit me? I really dont know…