My Boyfriend calls me mommy

I’m 20 my bf is 19, he always called me mommy as a joke and now I don’t think it’s a joke. For example he was talking about skipping his class and I said “good students go to their classes” and he said yes mommy. And I think it’s a joke but can’t tell? He has a horrible relationship w his mother because he is bisexual and his mom does not accept him. (I’m female btw). So I think that me being a female figure caring about him is like triggering is mommy issues or something ?? I have no idea