my boyfriend smells my armpits during sex

so lately ive been noticing that my boyfriend burrys his head near my armpit while we're having sex and hes smelling them. like yeah he has to breathe but he will actually move my arm up some more to get his face in there. the first time i happened i was like trying to get his head up bc it was hot in his room and im sure it didnt smell the best but he just pushed me away and went back to my pit LOL. he does have a foot fetish and told me its more hot when they arent washed, so maybe its like the smell of sweat?! i really dk but i wanna know if other people have seen this? im not shaming him in any way tho, it just made me so confused and im scared to actually ask him about it. sometimes i might have a little b.o smell cuz like i said it gets hot in his room, but idk if its that or maybe my natural sent really comes out there? also we've been dating for almost two years and he just started this, or ive just started to notice.