"Retroactive" generally refers to things which happened before the law was passed.
So unless the age of consent law in your area has recently been changed, what may be more relevant is the statute of limitations (the number of years after a crime during which a prosecution can be brought). That will depend on what state you're in, if you're in the US.
But yes, if it's within the statute of limitations, your boyfriend could be charged with statutory rape if your parents or anyone else wanted to report him.
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