@CommanderSalamander,
You told people your height based on what you had been told, that's not a lie. Explain it to them the same as you did here.
As far as supplements, routines and the such, that won't change a thing, especially at this late stage. Unless...
...do you have a stretching rack in the dungeon?
As Jespah said, genetics. Your DNA determined your height not the height fairy (a distant relative of the tooth fairy). If you are in good health, then slap a smile on your face and go out and live, live
Live.