Hello, I am 14 years old. I go to the gym about 4 times a week, and I have a big sexpack. (Not to brag)! And I was recently at the doctors for another reason, and they said it was unhealthy to gym that much. Is that true? I have no disease and nothing like that.
No. It's not unhealthy to go to the gym.
But, you must use proper technique/form when working out. Don't over do it either. If you try to lift to heavy a load or lift it the wrong way you can damage your bones/muscles.
Remember too, your body needs rest to develop. When you work out you tear your muscles and as they heal they become stronger.
Hope it helps.