Pushing my bf away??

Recently I have been constantly freaking out and worrying about my boyfriend leaving for China for two months. He leaves June 8th and I want to see him as much as possible. I've been freaking out and I believe it's been pushing him away. He told me today that he's scared to see me and hang out with me because something about me changed. I don't really understand. I tried to get him to explain how I changed and he couldn't describe how. The only thing I can think of is that I've been beyond worried and I think that has caused me to freak out more on him. How do I change this? I don't want him to be scared to hang out with me because I want to see him as much as possible. How should I act around him? Help!