You blow it

For whatever reason, probably impatience, Amy shifts suddenly causing he silk panties to slide across the sensitive underside of your shaft.

Your brain short circuits and the pleasure overwhelms you, and with one quick spasm, you dump your entire (still small) load onto the expensive panties, soiling the front of them with thick, white ropes.

"Oh my god." Amy exclaims, bursting into laughter.

"Hahaha, oh man. Oh my god, I'm so sorry. This never happens." You lie, laughing at the sheer idiocy of what just happened.

"Its okay, Joe, really. Its fine." She giggles.

"I'm gonna go get cleaned up, and we'll try this again."