If time suddenly started going backwards, eating and using the restroom would suddenly get extremely awkward...

So, are we physically committed to our past actions, but mentally aware of the time reversal?

For example: When the change happens, will I stand up from my desk, walk backwards to the restroom and watch helplessly as I unzip my pants and watch the water from the toilet fly up into my dick?

That's frightening.

And as time goes on, you'll get younger and younger, until the doctor has to shove you into your mother..

You're welcome, I'll be here all week.
- As time goes by, you'll forget more and more, until you lose the ability to speak, object permanence, your mother's face, and the ability to focus your eyes - at all.
  
  If there's any part of you that's aware of this process, it would be terrible. The worst part about having Alzheimer's, my father-in-law once told me, was being aware that he used to be more; that he couldn't remember things, but that he could remember once being able to remember them. I think it was a small blessing when he moved past that stage, and was merely angry and frightened at a world he just couldn't understand anymore.
  
  Wait... what were we taking about? Reverse-birth? You know, many civilizations didn't consider children real people until they were a couple of years old. Before that, they were just dumb animals with some potential; perfectly legal to kill. An adult horse has more self-awareness than a 1 y/o. By the time the doctor's shoving you back where you came from, you're barely human anymore.
  
  I can't wait to see the angry downvotes on this one.
Red Dwarf, “Backwards” (skip to 2m27s)
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- I wish I could upvote this twice.

Nothing says time has to go the direction we perceive it. It could go backwards and without a different frame of reference it would just be normal.

In my reality time moves forward with an acceleration of 10s/s^2. Time was at speed 0 at the creation of the universe.
- Them's relative measurements!

The Doughboys have been joking about this on their podcast recently. One of them remarked that in Tenet you would suck poop back up your butthole. So they joke that shitting is pulling a "reverse Tenet"

Suction is just pressure in reverse time...

Didn’t Red Dwarf have an episode that touched directly on this? I recall Lister having some very uncomfortable experiences

Yep. One of the funniest takes was that the people loved wars. It created population booms.