OK I'm only 15 years old and I weigh 110lbs. I workout and eat resonably healthy.

(approx 150 carbs a day, good carbs ie fruit) Why the **** do I have
STRETCH MARKS on my inner thighs and hips???? I've NEVER been over 112lbs!! They keep appearing, more and more... It is FREAKING me OUT! Is something WRONG?
Also, side note: If I eat and workout the way I do, why do I have a pudgy stomach?