It does sound mechanical to me. However it might be a good idea to invest in some good bras. At our time of life everything starts to head south so extra support, even for small breasts is a good idea. Over the years I've progressed from no bra, to maternity bras, then sports bra, regular bras and now I wear underwired bras. If I do go without a bra there is some aching.
Perhaps buy a couple of sports bras, and see how you get on.