You did the right thing by sharing your experience. Telling other people about things always helps. Perhaps you already feel some well-earned relief.
It's hard to know what really happened between the photographer and the model. I've been on both sides of the lens in the modeling business (never famous!), and it can take unexpected turns. I could tell lots of strange stories, but I'll save those for another time. It seems that the photographer definitely had sexual designs on the model. But was the model forced into what he was doing? Being asked to model in underwear was a hint that more might come. The model might be just having "seller's remorse" after everything was over.
There are lots of scenes in porn that we enjoy in the moment, but have concern about later. I sometimes enjoy "hidden camera" scenes where guys are showering or wanking in the toilet, unaware that they're being filmed. There is indeed something "wrong" about that, but I still often enjoy it.
I don't think you need to feel like a creep. We'll never know the full story here, so I suggest just taking it as a porn fantasy that you enjoyed. You mentioned your exams coming up--best of luck on those, and if you get to stressed, just give yourself a hand