Congrats on your weight loss so far!
Two words: weight training. Good old-fashioned weight training. With weights.
All else being equal, gaining muscle will reduce body fat percentage by definition, if you'll pardon the pun:
fat % / 100 = fat weight / total weight
= (total weight - (muscle, water, skeletal, connective tissue weight))/total weight * 100
More importantly, weight training -- if done properly -- will make you look fit rather than skinny-fat. It also lowers your risk of osteoporosis, enhances your performance in most sports and daily activities, and has a bunch of other health benefits.
I think I dropped below 20% BF the first time (i.e., Before Kid) after about a year of lifting, maybe two. But, it's going to depend a lot on your starting point (a bit higher BF% than me), your diet during that time, and your training program.
BTW, the online calculators are pretty terrible, as you say, and the Tanita scales (BIA method) are even worse. You may not be as high as you think. You might invest in a caliper test at your local gym, if it isn't free with membership, as a more accurate measure of where you are now.
Or, if you're good at self-assessment, Leigh Peele has an article on estimating BF percentages for men and women with pictures for comparison (all work-friendly). Or, go to the body fat estimation thread on Lyle McDonald's forum (forum.lylemcdonald.com, first "stickied" thread under General Diet Questions) and see if you can find pics + estimates for a woman who has a similar body type as yours.
//bstrong