How could I lose weight secretly?

Literally cut our sweets and high carbs, honestly this will work stick to foods with high protein and low carbs like chicken and have loads of veg and less carbs. You said your not fat? Well start doing weights to tone your body, focus on a kcal deficit as well.

Exercise doesn't cause weight loss. It's about your diet mostly -- try this: do not eat any foods containing sugar, switch to unsweetened almond milk if you must drink milk, do not eat refined oils only natural fats. Stop consuming grains of all types

i would just cut back on the junk food and exercise rnore