I should be overjoyed, but I don't know how to feel. Why?

Okay. 2 years ago I met this guy. I fell in love with him and loved him more than anything. He liked me alot and made me feel so important. He had to switch schools for 2 years. For awhile, I missed him so bad, I cried everyday. I was so sad and then I kinda got over him. Then I kept thinkin about him and the memories we made. He's comin back this school year and I don't know how to feel. When I found out he was comin back I started crying. I don't know why. I'm excited but I'm overwhelmed. I'm feeling different emotions with this. I'm happy of course but when I think about how he's comin back i feel weird and usually end up crying. Why?