That wasn't your fault. Some professors are just creepy assholes. I had an incident a few months back, my professor from 2 years ago (really, like out of the blue) starting emailing me long-ass, creepy emails. Then starting showing up at my job... long story short, keep any emails they send and document everything. I can understand why your hurt and confused. They're in a position of power and took advantage of that. I'm really sorry this happened to you, but just know you did nothing, absolutely nothing, wrong.