Everyone's different. I don't think my reply is going to be of much help - but my BMI is 18-19 (unsure exactly of my height), and a size 6 generally, sometimes size 8.
However, I feel a bit unhappy with my figure because I think my fat percentage or whatever has gone up, am actually "fatter" in comparison to what I used to look like and feel less fit than what I used to.
However, I don't know what your bone structure is, but as long as you aim for a BMI of 25 or below, you will be fine. : )