Sometimes I Just Want to pull out My Hair!

I am so hopping mad right now.......I don't know why Elizabeth feels the need to take off her diaper and play in it. Tonight I put her in her room for her to go to sleep for the evening. My neighbor came over to visit when Elizabeth starts hitting the door. I go and check on her and she is covered in poop. Not only that but her walls,carpet and favorite stuffed animals have poop on them to. It took me 30 minutes to get everything wiped off. Tomorrow I am going to have to steam clean her carpet and scrub the walls with bleach. I know Elizabeth has some challenges but I just wish she would stop taking off her diaper every time she poops or pees in it. She will be 4 this month and refuses to get potty trained. We have tried to duck tape her diaper put panties over it and we have even put her diaper on backwards. Her special ed teacher and occupational therapist have given me so many suggestions but none of them seem to work. I need a miracle to get his girl potty trained.