OH HI!! I couldn't respond since I couldn't log into my account... but here I am! It's been a long time since I've played this Underfell IF, but I think you have to look at the all videos in the lab to get to the Harem Ending. If that doesn't work, then I recommend clicking on all of the available options that are on the path you want to take (the options being the ones that don't kill you and seem relevant to the lore of the game. Like the books, videos and the multiple rooms you can access through the vents)
Hope this helps :3