Guys Help!!!! (girls too if you've been here...)?

My boyfriend and I have been together 6 months now, but we were friends for about 5 years. I seriously believe he could be the one (though I'm trying not to rush it). Every once and a while, when someone mentions being married or weddings, he says he's never getting married. I called him on it once in the car, and he said that it probably will happen someday, but he just doesn't want to think about it. So I let it go. But he still says things like "I'm never getting married/not having kids." I don't want to rush or anything - I like where our relationship is at and I'm in NO hurry to get married. But - I don't want to invest a ton of time and love in this relationship and end up leaving because he won't take that step with me - How do I approach this with him WITHOUT sounding like I'm trying to ask if he wants to marry ME and I'm just trying to broach the subject in general - HELP!!!