14 days late without period

Melissa • Hello my name is Melissa Bell and I was diagnosed with stage two endo this past august.
Well my blood test turned up negativie. I still don't have my period and it's been fourteen days. I am going to the doctor on Tuesday to find out why. I have been this late before. Also had four or five of the symptoms of pregnancy. So it's strange. Also had an ultrasound on my stomach and it came back saying I had a fatty mass on my liver. Would that be the reason I am late ? Any answers why would be great ! It's just weird because I have never been this late before. Hope the doctor will be able to answer my questions on Tuesday.