Son will only wee/poo with mummy and daddy

[debbie1g]

Hi, not sure what to do with about 3 year old son. He has been clean in the day for around 2 months and at home we rarely have any accidents. The probably is with Grandparents and at preschool, he point blank refuses to go unless Im there with him. He has been going to grandparents since I went back to work when he was 9 months old, so he is used to them changing his nappy and generally being at their home. Im now having to leave work to so he can go and then come back. Has anyone else had this, and how long did it go on for? We've tried stickers, reward sheets, sweets, bribing and nothing. We praise him all the time when he goes at home, which most of the time he does all by him self, so cant understand while he will then wait sometimes for 8 hours untill I get home. Any help would be appriciated. Thanks