Ok, I'm assuming at this point you understand that fat and muscle are two different tissues, just like your hair and your skin, correct?
Also, don't bother with the calorie counter on the treadmill. They are incredibly inaccurate and can give people a false sense of their workout (as in, "I burned 500 calories, so I can eat this donut since I burned it off")
I understand that you (like almost all women) feel that you build muscle quickly. While that may be so in relation to other Asian girls (not usually the most built girls), I can assure you, unless you have a serious hormone imbalance (which would be evident in other ways) - you will not just get all huge and muscular at the drop of a hat.
In order to actually build muscle you need
a.) a caloric surplus (that means eating
more than your body needs to sustain itself)
b.) sufficient load on the muscles (a strong wt lifting routine, or a lifestyle that stresses the muscles - think lumberjack, not carrying books or groceries)
c.) testosterone - men can typically build more than women b/c they have more testosterone. unless you have an abnormally large amount (serious imbalance), you will not just build a bunch of muscle with little to no effort.
Consider that men (with their higher levels of testosterone) must develop detailed plans of what/how much/when to eat, and stringent wt lifting routines in order to slowly build more muscle. Then you think you're gonna build big o' chunky muscles from carrying groceries? - If that's the case, go see your doctor.
Oh, and the thighs can feel all firm when flexed or stretched, even when they do have a lot of fat on them. If you can, get your body fat % measured by an experienced person. They are generally estimates, but you may be surprised.