Hey So Im 17 Years Old. I Train About 5

Hey so im 17 years old. I train about 5 days a week at a gym. i am a round 16% bodyfat so i am not ripped by any means. So when i was 14 i was fat and gaind stretchmarks on my hips and they have now turned white however i just recelty noticed a small red pink marn wich i think may be another stretchmark, it itches sometimes to. how can this happen? unbalanced hormones? Thx Adam 17