I Miss Her, and We Haven't Even Been Out of School for 24 Hours?

There's this girl I like at my school. She's in four of my cles and I see her every day. She's really cute and some guys think of her as the hottest girl in the school. She's currently going out with the baddest kid in the school, but I'm not sure how strong their relationship is. I have been talking to her more and more each day. I think she may know I like her. So, yesterday (Friday), we had a half day. I said goodbye to her and left, but that's beside the point. Last night, I couldn't stop thinking of her, which was normal because I always do. But this was a lot different. I literally had a stomachache and a heartache because of this. My eyes started to water and I took a pillow and held it like I was holding her. I think I might have kissed it once or twice, too. The pain has stopped, but I still have that feeling that I really miss her. Is this normal? What does it mean? What do I do now? How do I get over her? PLEASE HELP ME!