Becoming obsessive?

This girl came to my school a couple of years ago. As soon as we met I knew she was something special, Nit saying she was the one or anything. And we became best friends in a matter of weeks. It lasted like this for a year. Then, last month, she told me she loved me, always had and she wanted to have a serious relationship with me. We'd done sexual stuff before, and she invited herself over. She took herself up to my bedroom, and she put her hand on my leg, slowly moving it up to my crotch. She put her hand on my dick and I put my hand on her boob. We kissed for a while and then I went to take her top off. She said no, but her actions spoke otherwise and she lifted her arms up. After we'd finished fooling around, she told me she didn't want to do it and left my house. She walked to her ex-boyfriends house and told him because she was upset. Besides the fact that he hates me and she won't talk to me, I found myself obsessed with her. I've tried myself to become unobsessed but I still miss her so much, as a friend, and more. What I'm asking is, is it normal to be so obsessed with somebody you don't listen to them? I know not stopping was wrong, but I need help to know if what I did wasnt normal.

Thanks in advance :)