I think I'm losing my boyfriend?

I'm worried I'm losing my boyfriend. We've been together for 6 months, and I love him a lot, but I haven't told him I love him. I think his liking for me is decreasing. Whenever we make eye contact, he tends to look somewhere else. He doesn't text me anymore or aim me anymore because he says he doesn't like doing that. I'm worried he might like some other girl, as to what I see on his aim. It says, "she's such a charmer, oh no..." He and I only see eachother at school. I don't know what to do...I don't want to lost him.