I think it has to do with your shape too....when I weighed 125-130 I was in a 7/8 to 9/10 depending on the cut, my 18 year old daughter is 125-130 now and has a different body shape than I did and wears a 3/4 and sometimes can still squeeze into a 0/1. People can't believe she actually weighs 125-130 but she is very muscular and medium boned but looks much smaller. Luckily she inherited the skinny all the way to her chin legs from her dad and not the curse of the hips & thighs from the onset of puberty like me.
I'm 5'8", will be a size 12 when I get down to around 155 and would be a size 10 if I ever got as low as 135. So basically there is no possible way, with my body shape, to ever be a size 6! I agree with Wyllenn, I think it's best to keep losing until you feel comfortable and happy with yourself and know that you can maintain.
Like everyone has mentioned it depends a lot on your frame and muscle mass. At 5'8'' and 150lbs I usually wear 6-8. When I get closer to 140 it's more 4-6's. It could be reasonable for you but I would say just keep working out and eating right and judge for yourself as your body adjusts. Good luck.
Thanks for all your responses. I'm not wedded to being a size 6, in fact, I was wondering whether that would be realistic cause I haven't been a 6 since my last year of HS and my hip boness have grown a little in the meantime.
Frame does matter. I am 5'2" and my goal is 130 lbs. That would put me in a size 8 pant with a medium shirt size. I am never a small, even at my goal weight.
Frame is a big, big thing. At 5'7" it is much more likely to wear a size 6 jeans if you are an "apple" type (you carry weight up top and in the belly, but have small hips and legs) than it would be if you are a pear type or an hourglass. (Where you tend to be curvier in the hips and legs.)
I am 5'7", and I have not been a size 6 in jeans since I was in JUNIOR HIGH-probably about 8th grade. At my lowest adult weight, about 135-I am about a size 8 at that point, but 135 is a very, very hard weight for my body to maintain. I can hold 140 a lot easier, and healthier. So, for me, at 5'7", a size 6 is not realistic-but a size 8 is doable with a lot of hard, hard, hard work.
Frame is a huge, huge thing. Small framed ladies can more naturally become smaller-but medium to larger framed ladies at that height, and depending on their body type/shape, not everyone can be a 6 at 5'7" tall. My stepmother is 5'11" for instance, and she is thin and willowy at about a size 9/10-11/12, with legs that go for miles.