I wore this under a vintage t-shirt and realized barely even halfway through the morning that I was falling out of the bra. I am a 36E (DDD) and bought according to the skims size chart. It’s a very comfortable bra, but maybe too comfortable if you know what I mean. Sizing up would create a separate issue of the band size being too large, but falling out of the cup is also a major issue. I can still wear this at the beginning of my cycle (under an adequately lined top) and not have the same issue. I would recommend trying this when your fluctuating up rather than down, just to be sure.