Check the local listings in your area for Lingerie Shops. If one isn't available, then try a major department store. All have experienced bra fitters.
I prefer the lingerie shops though. Since this is their specialty, you'll receive personal care from the time you arrive until you leave.
Not only will you be fitted properly, but they will find bras for you, that will remedy the issues you have. They will also come into the dressing room with you (after you've tried on a bra) to make sure that the selection works for you; if not, they'll bring more to you. You'll need to leave your modesty at the door, but you will be oh so, ever so satisfied!!