Why do my boobs hurt?

I'm 15 and my boobs are 32DD, I know this isn't yahoo but why do they hurt? They never hurt and they are already grown in.. does it mean they are growing bigger if they hurt? My period should be coming, but it is not here yet. This is the first time they hurt in the past 3 years and since they are already really big, I don't think they should be getting bigger. Please help! :) thank you
Why do my boobs hurt?
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