Late period 😣

Tahlia • ✨👽🍃
My period is 13 days delayed now and it's never been this late. I'm quite regular and  usually before I get it my boobs are super sore and I have light cramping but haven't felt either of those so I'm getting super worried. I've taken 2 hpt's and even gone to the doctors to get a blood test and all have came back negative. They said if it still doesn't come in a week to go back to them. 
Is there any chance the blood test could be wrong though?