If you are at the stage where you are discussing moving across country to be with each other, wouldn't it be the time to say "I love you?" I think so. I know I would be expressing something as important as love by that point.
I think if I were in your situation I would be really casual about it and just say, "hey, I know we haven't said this before but I just wanted you to know that I really love you and here is why... thanks for being there and being your awesome self. What every happens I just wanted you to know what you mean to me." That's it.
I don't know, I think people get too hung up on the "I love you" thing. I love tons of people and tell them that when I feel it. I think that really we say "I love you" in many ways that are just as valid anyway, so occasionally popping that in there is no biggy to me.
Ya, over thinking as far as I am concerned