tight abs V loose abs advice

pearshapedmum

I was wondering whether someone here might be able to help me. Back when I was very fit, my side profile showed a perfectly flat stomach which looked the same as when I tensed it. Now however (25lbs heavier) if I look at my profile and relax my stomach somewhat, my abs look quite a bit distended/rounded but then when I tense them up they look nice and flat again (albeit apart from the roll of flab under my belly button). Do I need to do more core strengthening exercises to fix this, or is this permanent result of having had a baby 5 years ago?!

all opinions welcome!