Do I really have that much weight to loose?

I'm a 5'5 female I weigh 8 and a half stone my bmi is perfect. I eat relatively healthy and exercise a couple times a week. I look really slim everywhere except for my waist line? My waist is currently 34inches which means I'm overweight but I fear if I lose any more weight I'll look sick thin because the weight leaves everywhere but my waist line? My goal waist is 30 inches according to my BMI but how do i loose 4 inches that is a lot? What can I do? And how long would it take?
Do I really have that much weight to loose?
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