SARMs are milder than AAS, and you're right, cardarine isn't hormonal. But still, I don't think anyone will recommend that you turn to SARMs at age 17.
It seems like you could lose a fair amount of weight just by controlling your diet and doing preseason training, especially with all the hormones you have at 17. Use a calorie counter to see how many calories you should eat for your weight/activity level, and break your macros down into the following:
carbs - 1.0 per lb. (can vary based on metabolism, workouts, body type)
protein - 1.0g per lb.
fats - .5 per lb.