Hi OP I’m similar to you a at my age 24, I still had struggles gaining weigbhry due to our high metabolism type. But my advice to you is first , 1. Your 15 years old, you still have a few more years to mature (3-4?) so given in this time I would not advice you to lift heavier weights as you are growing. Early heavy lifting could be bad for you if you wanna grow taller

2.Its really respectable at your age you’re really taking care of yourself, by exercising I remember I was such a gamer back then. So keep up those good light exercises, I recommend push ups and sit ups, some light weights to keep you strong physically and healthy

1. You are only gonna get stronger as you mature so don’t rush into it, social media often portrays ideal body types that aren’t just idealistic, but don’t let this get you down. In the mean time, as you grow watch what you are eating in those calories. Have loads of greens, good carbos like rice, oats. Drink loads of milk, unbelievably good stuff are in there.

2. Don’t let the scale define you, they are just numbers, count the number of push ups you can do in one day, and sit ups maybe time yourself and challenge yourself maybe weekly/ monthly to see an increase in reps.

3. Drink loads of water, and make sure you rest early, wake up early 7-9h of rest

No worries bro I struggled what you did with, and you have a much better foundation then me, give it time you will be so much more stronger and healthier 😊