How to get over someone you've never actually been in a relationship with?

Everything just seems so crazy to me right now. I know, it might sound pathetic to care so deeply about someone who probably never knew, but im stuck. I don't know where to turn. This all happened so suddenly. I swore that we had something going on, but then it all changed. When im with him, we can talk for hours and hours, but then when were with a certain group of people, its like i don't exist. And it wasn't like that until maybe like a few weeks ago. Or maybe it just took me this long to notice. But then, when there gone, its like, oh, lets me best friends and call and text all the time. But now i realized it and im like, no, im not some second choice or something. I don't want to be the type of person that he uses b/c he knows im always gonna be there. I try so hard to stop, but think about him so much that sometimes i don't even notice im doing it. Is it really sad that i made someone basically my everything, and now im nothing? is it wrong for me to be cynical about love And believe that its all a sham? please, please help me. I know its sorta long, but i really need someone to give me advice. I don't know who else to talk to.