first of all i think that if you keep going with your healthy regime and focus on exercises that tone the stomach area then you should see some results come summer - from your picture you don't look like you need to be quite so insecure.
Anyway, if you don't feel comfortable in a bikini i would suggest either a one piece swimsuit or a tankini. if you have a big boobs then make sure it has good straps (so you don't scare the children! lol!) i would recommend a halter-neck style as they also balance out the hips and draw attention away, for instance from your stomach. underwired cups might also be good to look at but with most retro and vintage styles they tend to define and support that area anyway. with a swimsuit your stomach will be covered and you could get one in a really cute polka dot print, or perhaps with ruffles, or piping (see link) which will also define your curves: http://www.ivillage.co.uk/beauty/fashion/picturegallery/popup/0,,716031,00.html
if you like retro style then you should like something like this jasmine guiness swimsuit from oli, and if you click along there are 12 different styles that can inspire you as to what you'd might like.
on the otherhand you could opt for a tankini which will show part of your stomach, but really aids in breaking up the area although i find these can be quite annoying especially say at a water park as they tend to ride up.
also, they still do sell the bikinis with high waisted bottoms, they came back into fashion only recently, i'm not sure exactly where you can get them from, the address below will take you to a blog, scroll down and the one before last has two pictures of the style you're referring to and you can actually go on the websites to buy them (they are US though, you didn't say where you were from) http://www.agentlover.com/blog/2009/04/16/on-the-search-for-the-perfect-retro-bathing-suit-the-sequel/
hope this has been helpful
searched "retro swimwear" on google - there are loads of sites that sell retro inspired swimwear