Hi Anne Marie,
I am sorry to hear this, this is so nerve wracking. I know that with the holiday approaching it will be probably impossible to get an explanation as to why they need to do another MRI. It may very well be some sort of error on their part, i.e. they might have missed something. I know exactly how you feel , having gone through the rollercoaster recently, only to find out that there was some miscommunication between the radiologist and the GP. Hang in there. Try to have a good Easter weekend with your family and not to think too much about it.