Postpartum weight loss

Precious

So I just had my daughter in June , ivebeen walking atleast 3-4 days a week on my treadmill and I can't seem to lose a pound . I really just want to lose about 15 pounds . I'm 4'10 1/2 , I'm almost 19 and now I weight about 146 pounds . I would like to be atleast 120 pounds (my weight before birth) . I'd also like to make my butt bigger , considering pregnancy has literally made it flat . Any ideas or suggestions?