How can I let my girlfriend know that I really miss the little things she used to do for me?

My girlfriend used to send me IMs when I was away and she was thinking about me and called or texted me when she was. But lately she doesn't do those things as much and I really miss it. I think I always tried to show appreciation when she did those things by messaging her back and I always mentioned how sweet it was when she called for no real reason. So how can I let her know that I miss it without actually telling coming out and saying it? Should I be concered that she doesn't because I know she loves me very much.