Stress, Pregnant or something wrong

Has anyone had a period that was two weeks late and not been pregnant?

I've taken to tests, both negative and a blood test that's negative..

Apart from stress is there anything that could cause it?

The doctor said there was nothing wrong unless I do extra checks on my liver or ovaries..

Is there a chance something bigger is wrong or do you think I could be pregnant and I could be one of those people who don't know they're pregnant until pretty late ahahha