Our situation is a little bit different. We've been trying for awhile, but so far we've had no luck. In my situation, DH would want to know ASAP.
I think V-Day might be a little too much, but only you know your SO's "ick" factor. My DH would think it's too mushy to spring it on him on V-Day. He'd never would have proposed on Christmas or V-Day. We're too cynical as individuals and as a couple.
So do what you think is most appropriate.
!!!! Congratulations !!!!