What's the best way to go about defining a romantic relationship?

I’ve been seeing a guy for a couple months now. It’s well established that neither of us are interested in pursuing other people, we spend a lot of time together, and we really like each other. In my eyes, we are already boyfriend/girlfriend in all respects. However, he has yet to clearly define the relationship as such. I’ve been patient because I don’t want to pressure him and feel that I shouldn’t place so much emphasis on the label. At the same time, though, I would feel more comfortable if our relationship was “officialized.” Should I keep waiting for him to bring it up when he’s ready, or should I speak up first?