<human>: Could you distill the essence of the text into 1-3 sentences?

So, I'm dating a very nice guy but we're not exclusive. He's a real catch... Looks like a model, handsome, funny, and usually very sweet. We usually spend at least two nights per week at his house (go out for dinner + breakfast), when I travel he says he misses me, etc. In general, he's not someone who doesn't want commitment we've just never really had that talk (or I guess, since we started going on dates again.) I'm certain that he still flirts with other girls and is talking to other girls and I think he has been on dates (couple of nights he randomly didn't talk to me at. all. this week and then he goes back to hugs and kisses and heart faces. My guess is likely he had his phone away because he was with girls.) 

I'm not the best at communication. I get scared to put myself out there because I don't want to be rejected. He also literally looks like a model and I'm...curvy. Overweight. I know he's attracted to me but I know he's dated a lot of girls who are more "equal" to his appearance in society's perspective. But he's also strangely not aware of how good looking he is. He's had some health issues and doesn't have much confidence.
<bot>: how do you go about having the talk to tell someone that you want to be exclusive and that you may walk away if you're not moving in that direction?