Basically I desperately need fic where Jacob is in denial about wanting to be with Newt but refuses because he can't see himself as anything but straight. Newt offers to do a potion/spell that will change his gender at least for one night so they can have sex and Jacob can be happy.

And that's fine and all, Jacob is thrilled and female!Newt is hot as hell and the sex is amazing. But he ends up counting down to the time when Newt changes back into a dude because he prefers that Newt and realizes he's happier fucking him as a guy.