My son who is 30 months old is just like this. He follows me to the bathroom and will not allow his father to do anything for him at all. It does wear you down after a while but giving up work is not the solution. It is good for little ones to be looked after by a variety of friends and family and this is were I made the mistake. My husband was not a very hands on dad at the start and I did everything for my son. I don't think it's down to a lack of confidence but your daughter may not yet have realised that she can trust anyone apart from you. I'm sure this is just a stage they all go through and if you just persevere it will pass in time.