If there is a median size, then half the men are under it. The only reason your coworker would be laughing behind your back about it, is if she was a shallow person - at that point she’ll be laughing about a lot more - height, looks.

At the end of the day, you cannot change your size, anymore than you can change your eyecolor, regrow hair as a bald person, etc. Ultimately, nobody cares about your dicksize, the only person that might is your partner, and even then it’s a prefference. A partner will never check all the “prefference” checkboxes either, since a partner that is “perfect for you” isn’t some magical entity that was created by reading your mind.