I don't know if this is something that started happening after I breastfed my kids but my nipples poke out of my bra, so if I am wearing something like a tight shirt my nipples show and it is very embarrassing.  I have bought some bras for when I wear t-shirts which have some padding.  Doesn't have to be like a pillow but some padding in the cup and this solves the problem.  I really thought this bra was like that and it has zero padding.  I kept it because it has a good fit and it's comfortable but it doesn't offer me the coverage I wanted.