I have 2 kids - both whom I breastfeed for 15months - so I need a swimsuit with a bit of support at top and also tummy not flat any more. I am a size 12. Everything is either something like my mum would wear or biue (which I don't like).
You need a boob measure sized halter neck tankini. Seriously. I had one from John Lewis and it was the first post twins swimwear I tried on that made me feel good about how I looked, so, so worth spending more than you are used to to get something good. Halter = boob hoisting/shoulder flattering, tankini = break up shape over stomach area so no bulgy looking tummy in a one piece. black and white polka dot stripy