My daughter is almost 5, she will use her little potty chair for pee pee( she has never poop'd in the potty) She will vomit at the sight of poo or pee. She's afraid of the big potty and will totally freak out if she has to even go near a public bathroom... I sometimes think she got this fear back when she was at a doctors visit and we had to hold her down and force a catheter in her and when they pulled it out, urine went all over her and she vomited. She has had a few catheters in her to collect urine because she wouldnt potty in the cup and shes had quite a few UTI's. She did end up having surgery at age 4, almost a year ago for kidney reflux.
I cant get her to have a bowel movement in the potty.. I cant get her to go into a public bathroom.