There was a porn star one, but again that was all human. There was one by Mrs Muir that is Spike/Angel/Buffy where the first time is horrible but mostly because she's still a virgin and dry and it's difficult and Angel was there too. It sounds bad but it's a great story, trust me, and is mostly spuffy since Angel can't sleep with Buffy on his own.
Three Hearts Entwined by Mrs Muir if anyone is interested in that one. But it doesn't seem like it would be the one you're looking for since I think Angel being around would be a big clue you would mention.
It's such a PWP theme, 'Oh! You're so big!', that it's hard to think what story you could be searching for.
