How long till i see changes in my body ?

Im 15-16 in 4 days haha im 120lbs. And 5'2 & about one week ago i started working out everyday toning /cardio. eating pretty healthy too. ive lost 3 pounds so far. but i still havnt seen much of a change yet. and its so frustrating. .How long of keeping with this will i see my flat belly?? :) tyy