Late period/negative test

Elizabeth
Hi all
I'm completely new to this but just wanted some advice. I normally have a cycle that I could time my watch by. I'm never ever late. 
I'm now 6 days late but took a test this afternoon and it was negative. I don't feel too different, maybe increased appetite and bloating. But I can't think of any other explanation for my late period. 
Has anyone experienced this? Should I take another test at a different time and how long should I leave it? 
Thanks in advance for any help!