21 Month Old "Afraid" to Poop

She isn't constipated yet, but trust me, this is how it starts. My guy did the same thing until he was constipated, and on the verge of developing encopresis. You need to make sure she's eating lots of fruits, veggies and whole grains, plus drinking lots of water so she needs to go poop every day, fiber gummies help as well. If she gets to the point she's held it and becomes constipated it will hurt when she goes, and then she will hold it for that reason and this will be an even bigger problem.

A site I recommend explains that children under 5 think they can hold poop in and make it disappear, they don't understand until 5 or older that it isn't going to go away or that they need to poop and are hurting themselves by trying to hold it it. Check out the site, it is a wealth of information on potty training problems and will hopefully help you get her on track:
http://www.rogerknapp.com/medical/pottytrainingrefusals.htm
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And while I realize you say this isn't a potty training question, it truly is as pre-training all goes into her eventually being potty trained. Toddlers and even preschoolers can't separate in their minds and know that this isn't one whole picture and see it simply as not using the potty vs using the potty, to them pooping is pooping, period, it all goes together. Each child is different in regards to how they will potty train, even within the same household, I have trained many children before my last a year ago and I still learned things I wasn't aware of that helped me get him there.

Some kids feel that they are losing a part of themselves down the toilet. Try talking with her about how this is waste that her body wants to get rid of so that she can be healthy.

A potty chair might help. The poop goes into a container and doesn't disappear. Wait until she's gone before flushing it.

After your SWH I suggest it's possible you're giving this too much attention. I'd try not paying attention to when she's holding it. I suggest that if she doesn't get the attention/pressure her body will expel the poop on it's own.

I'm a little confused. You said you had already "backed all the way off" on potty training so I assumed that meant she was in diapers and you weren't trying the potty at all -- but it sounds as if she is expected to go on the toilet if you are saying you "sit with her." Which is it?

She does not sound ready at all. There is zero shame in putting her back into diapers until she IS ready. And the fact she is sick is very significant -- she is cranky and tired and feels bad, and is in no mood to use the potty, so leave it until she is both well and interested.

It will not ruin her chances at successful pottying later if you backtrack and do diapers now, especially while she's ill. Don't frustrate yourself and her too.

As someone else noted, kids this age often fear they are losing "part of themselves" down the toilet when they poop. So they become frightened to use the toilet. It's a common obstacle to potty training for bowel movements.