Did the dog eat that box of chocolates you bought? Or is your love on a higher plane of existence than can be expressed by mere candy, champagne, diamonds, lingerie, sonnets, teddy bears, flowers, and fine dining?
Then Wolfram Research has just what you need: Equations for Valentines from the Wolfram Demonstrations Project!
(What other Valentine comes complete with source code?)
UPDATE: See also A Valentine's Day Surprise.