Sorry to be blunt, but have you seen a therapist to see if you aren't developing an eating disorder? It doesn't sound like to me that you need to lose any more weight either. I can assure you, many, many women will be bigger than you are if you go to a typical family beach or such place. Size 12 is considered average. Of course, that does depend on height.

I wear a one piece (size 14/16) and wear a pair of exercise shorts on top of it--and I go to the beach!