Eat healthy and exercise but still fat.. where am i going wrong?

ok i hav a little baby who is 18 months, and i am a size 18 (uk size) and quite tall. all my fat seems to be round my belly and thighs. i eat cereal in the mornin with fresh orange, then at dinnertime i have a sandwich, a yoghurt and a banana usually. then for tea i have meat such as chicken or pork or summat with potatos and veg. then have some dried fruit in evenin as a snack. i take my baby for walks everyday and altho im doin my best im stuck at size 18! i rarely eat crisps n stuff. i do have a takeaway once a week but i try to get a healthy option- so if i have fish and chips ill take the batter of the fish, and i wont eat all my chips to save calories. some weeks we dont bother with a takeaway. where on earth am i going wrong?