I can't anymore.

My daughter, who turns 5 in 2 weeks thinks it's okay to poop on herself. She just stands there and poops on herself. She says "I'm too busy" and "I made a mistake". I've tried being gentle about it but then when she does it again she says "my mommy says it's okay to poop on myself because everyone makes mistakes." I can't put her in a pullup because A. she won't go potty at all & B. she's too big for them and the bedtime pullups are too expensive to use as a pullup. she was fully potty trained as well as night trained. I don't know what her deal is but I cannot do this with her anymore. she now sneaks that she pooped on herself but we find out because she doesn't wipe and she smears it on the toilet when she poops and "goes potty" and changes her clothes when she's done. what the heck can I possibly do to make this stop?!! we took her to the doctor about it and they said she was constipated, gave her miralax, and we had a week of hell where she was hitting and punching me (I'm pregnant as well) and her 2 year old sister, screaming at us and threatening to call the cops to save her. All because I'd ask her to go potty, or no to something at the store. causing a scene and running away. I don't know what to do with her anymore and honestly it's making my life hell.