If you really want to wear it, you can go to the tailor's shop and see if you can exchange it. If it doesn't look good, you can wear a small suit or something outside. You don't have to have a thin chest! Personally, I think that girls' breasts are their own. To accept their health, it is not necessarily thin breasts. If you want to be thin, you can do some exercise and eat healthily. Or you can gently tell your boyfriend to buy bigger clothes next time.