"On my 14 carats" is an
expression used to indicate when a female is ovulating (most fertile and likely to conceive), which most commonly and predictably occurs on the 14th day of the 28-day
menstrual cycle. The expression can be used either in flirtatious seduction or as a warning that birth control should be considered to prevent pregnancy. The expression went viral when Selena Gomez used the expression "I'm on my 14 carats. . ." in the very first line of her seductive song "
Good for You," the video for which clearly shows her writhing in the throngs of umcontollable ovulation.