Yeah Jay has sound advice there.
This happened to me about 2 years ago with my ex... luckily I'm good with my fingers and just blagged that I wasn't really up for it... Whether she bought this or not who knows! Orgasm is orgasm at the end of it all!
Anyway, the next time it was all good, I just took it easy and sure enough hard as a rock I was.
Try not to think about it so much next time and just go with the flow man, you'll be fine trust!
P.S if this becomes a persistant problem try poppin' a V!
It's happened to us all at least once, right?
Ritz