my boyfriend is possessive and might get mad at me if I went along with a male friend calling me that
Honestly, I think your boyfriend has a problem, not that my opinion matters much. Possessiveness is bad. I would feel far more sexually/emotionally threatened if someone actually
wanted to possess me than someone playfully and insignificantly saying "my" to me. I don't understand why you think that actual possessiveness from your boyfriend is more acceptable than something unserious from someone else... after all, you said that saying "my beautiful" is unacceptable even before the fact that you have a boyfriend. Well, on second thought, I guess you could say you gave him permission to be possessive first.