I have hit my all time low (from what I can remember): 146lbs. Back in 10th grd I lost some weight and was at 148lbs, and then gained it all back. However, looking back at pictures of me at 148, I seem to be a bit smaller than I am now.. which makes absolutely no sense to me.
I find that weight sometimes settles in different places at different times--and one's body as a teenager is different from one's body as an adult.
That said, exercise is very likely to be the difference. Were you more active as a teenager than you are now? Muscle is more compact than fat, so if you were more active and carried more muscle, you'd look a bit leaner than if you didn't.
__________________ "Losing weight is easy; I've done it dozens of times."
Your body structure would have been a lot different in 10th grade than it is as an adult women. In 10th grade, your body would have still been changing and growing. This is why there are "junior" clothes and "misses" clothes. Adolescence and adults have very different bodies, hence the difference in the pictures even though your weight is the same.
It's not that some people have willpower and some don't. It's that some people are ready to change and others are not.