dick size

so I have only been with one guy ever and only seem 1 dick ever and I have been with my bf for almost 9 months now. and when he's hard he looks big (dick) and when he's soft he still looks big but I know this is prolly a dumb question but how do I know his dick is like nice? like he's circumsized and I just feel like it would be really awkward to ask him now what his size is lol. help I guess or advice