Why can't I stop thinking about her?

So me and this girl have been talking and texting alot. We flirt with each other and joke around. So the other day I guess she gave me a hint that she liked me but I'm not too sure. But we continune talking and seeing each other and I notice that I'm falling for her. Every day when I wake up I have a text from her and It drives me crazy. I mean I love texting her except it makes me think of her. Every second of the day I'm thinking about her and I can't stop. She such a distraction for me. Even in school I'm having problems because I can't focus because of her. And plus she left for the weekend for a camping trip and she couldn't talk to me. So the weirdest thing happened. I looked at the ceiling in my room today and all the dots formed her face. It was strange. I need advice