Sexualization of breasts

Literally my boyfriend along with his mother find it inappropriate that I don't wear bras. For a fact I just got off FaceTime with my bf and he goes "I hope you're not leaving the house like that" because my sleep wear tank top is see through so he could see my nipples. I've spent so many hours trying to be patient with him and his mother, explaining boobs feed babies that's it, they aren't sexual organs, so stop sexualizing them..? I am actually worried I'll be shamed for breast feeding and or forced to feed in a room when I visit. Opinions and or advice please