Due date changed


How often do docs change your due date and why!? So first when I came in at 14 weeks I told them my last period ect. Doc still gave me due date a week later with an ultrasound. June 1st. Now after my 20 week ultra sound I ask for a proof of pregnancy for insurance purposes and I get paperwork stating my due date May 17 ? I'm really peeved at this point. I do need my rogam shot and my glucose test done and it just seems like my doctor isn't really consered or worried or cares to have everything in order 🤔.