Thanks for the advice nycindie, I really appreciate it. And you're definitely right that treating it like a Big Freaking Deal is probably the wrong way to go. I'm torn on whether going the nonchalant route is a good idea or not though -- I think he's going to have some concerns, and I want to reassure him. It seems like it would be easiest to do that by having a direct conversation. Just maybe even catching him on google chat and saying something like "Hey, there's something I've been wanting to tell you. I want to say first that I'm really satisfied with our situation and don't need anything to change and don't expect anything from you. But I do want you to know that I love you. I've just been wanting to say it for a while.
But I don't know, maybe you've got a point! You've certainly given me food for thought.