overnight dental cavities????????????????

I'm a 17 yr. old teenage girl, and I just had my cavities fixed less than a week ago. Suddenly,l today I was looking at my teeth and saw this hole. Its now wonder I felt weird when I was eating. I've always brushed my teeth and flossed after my last dentist appointment. Then suddenly there's this hole. I'm really confused. I thought it takes a while before a cavity can form. But it seemed like that this one formed overnight. What to do? Can a cavity wait three months if i really take really good care of my teeth?
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You should call your dentist and tell them what happened
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