I'm in agreement with kiwi that it sounds like you need to have a family doctor or adolescent medicine doctor (primary care doc for teens) monitor your health and weight.

I wouldn't imagine that having ADHD and taking Adderall (I read your profile) would make it easy for you to gain weight. You may need a meds adjustment or if not that, then help from a nutritionist to help you identify ways to gain weight. Like super-high-calorie diets. I hear you when you say you already eat a lot.

I have a niece who takes meds for ADHD and seem to have stunted her growth a little. Her ADHD is fairly mild, but her meds have caused her end up much shorter than her parents were expecting.

I think that those who prescribe psych meds would do well to pay more attention to the potential harm that those meds may be doing to the physical health of those they're prescribed for.

So...I hope your parents will be agreeable to letting you find a primary care doctor to look out for your body's welfare.

Hugs.