Why do I not look like I weigh the amount I weigh?

Anonymous
I'm 14, 5'3, 137lbs, wear a size 4-6 us for dresses and shirts and a size 6 or 7 for jeans (8 or 9 if the jeans are very very tight fitting) with measurements 32-27-35.5 and yet people assume that I weigh 120-125 because I'm pretty fit. I have a half inch bulge of fat on my lower abs and I have a pretty big butt and my thighs are average and my calves are very well defined. I workout 4-6 days a week on average and I eat healthy. But why am I so heavy when I don't look it? I can't drop the weight because I'm recovering from an eating disorder and my mother wants me at 140.
Updates
+1 y
I am now 5'4
Why do I not look like I weigh the amount I weigh?
8 Opinion