It's actually not healthy for most women (I am assuming that you're a woman) to have a flat stomach. It's normal to have a little mound for a stomach. It's just a modern myth that everyone should have flat stomachs. Check out all the ancient Greek statues of Aphrodite the goddess of love - who is supposed to be the very example of absolute beauty - and nearly all of them show her with a belly that isn't flat.
I'm pretty certain that 120 pounds is within the normal healthy weight range for someone of your height. You could try to make your calves a little leaner by doing exercises that target strengthening them, but it sounds like you are beautifully healthy and are just caught in the trap of the modern beauty myth where the media (celebrities, models, etc) are telling you you need to be thinner and smaller everywhere when that's only healthy for the minority of girls.
do ab workouts for the stomach but the reason your not loosing weight is probably because your gaining muscle mass which is heavier then fat when working out think more on how you want you body to look and less on your weight. You are the average weight you need to be.
Your BMI is within normal range, so I would not advise trying to lose a bunch of weight. If you want to tone your body, then do strategic exercises for those areas. Like for the stomach, do crunches and other ab work outs. For the calves, do calf lifts(standing on the edge of a stair with your heels hanging off the edge and then go up on your toes and back down again, then repeat). Try to remember that muscle does weigh more than fat(all body builders are considered "obese" according to their BMI). Keep up with eating healthy and do exercises that will target the areas you want to change.
Thank you for your suggestions!