Read it probably 100 times not sure if it was removed from ff.net at least that's where I thought it was but my computer died last month and I lost all my bookmarks.

The premise is that Buffy and Spike go into another dimension to save Angel, I believe Wesley stays behind at the end of the story as he's fallen for someone in that dimension help!!

Could it be Strange Days and the sequel Homesick by theslayer19. Both the stories are on SR.

Thanks but not it

I feel like I'm losing my mind.

I think that's Marking Time by Annapurna_2 or Night Owl. It's here on TSR

Only it's Gunn who stays behind.