How do I finally let go of him?

First let me give this guy a name- Davey. Ok I go to school with Davey and he's a year younger than me. I first started talking to him last December. I told Davey that I liked him, and he told me that he liked me too. So we talked until around January 15 or so, because he just stopped talking to me for no reason at all. In february we became friends again but only text every now and then(not a lot). Monday at school we have to switch homerooms, and Davey is going to be in the same one as me. Well he texted me today and when i saw his name i started shaking and just felt so nervous. Every time see him I get that feeling and it wont stop. I'm not over him but i need to. How do I get over him, because when hes going to be in my cl Im going to have to see him everyday. How do I finally let go?