Should I confront my teacher or not?

I'm a freshman at highschool. When I started school I saw a very cute guy (he must be about 26) who was a teacher at the school (he isn't really my teacher, he doesn't teach at my classroom), we kinda liked each other, we exchanged smiles, we chatted a little bit. I'd remain there late hours after school just to get a glimpse of him. One day he saw me, halted me inside one of the rooms, picked me up and kissed me for about 15 minutes. I felt very scared but could not resist. Then I was like OK because he'd send me a rose or a note almost everyday through other students and this kind of stuff but I fell sick (I got measles) and couldn't come to school for a long time. When I came back he'd hardly say hi to me, he didn't care about me at all, I would cry all day long. I learned from a classmate that he was now dating a girl from another classroom, maybe because she's older and closer to his age but this really freaked me out. HE knew that I liked him and now he's with another girl from the same school, he should be respectful at least towards the young girls who are his students, if not towards the school where he works… but He did exactly the opposite. I feel so pissed off I sometimes think I should confront that girl or him but I'm not sure, I feel fat and ugly.