Spike is married with a mistress Buffy

Hi! I tried to search so many sites and the forums here and had no luck finding the fic I was looking for. I've found similar searches and they have either not had enough information for me to determine if that's the fic I'm looking for or they haven't been it. You're my last hope!

Spike is married (maybe to Drusilla but not 100% sure) and he's not very happy with her. He ends up meeting Buffy somewhere and they begin to have an affair. She doesn't find out until much later and after it's already too late and she's in love with him. Eventually Drusilla decides that she wants to have a baby with Spike and it freaks him out and sends him back to Buffy in a panic. Drusilla also knows about Buffy but doesn't let Spike know. She hires someone to kind of spy on Buffy I guess. I can't remember if it's Riley or not that she chooses. But one night Buffy is out with this other guy on a date and they run into Spike and Drusilla out on a date as well. I also think there might be some sort of blackmail going on where Buffy ends up at the mansion where Spike and Drusilla live but I'm not too positive.

I hope I've added enough information for someone to recognize what fic this is. Any help would be greatly appreciated!! Thank you!!!