8 days late? 2 BFN's

I'm 8 days late for AF
​Taken two tests (one on 25th and one on 24th) haven't taken one since but they were both BFN's. 
​I'm usually like clockwork! I never ovulate late and my periods are always very very regular if not early by a day or two sometimes. I'm so anxious too it's like a long anxious waiting game! 
​I don't track BBT or use OPK's. 
​I'm very confused, could I still be pregnant?
​When should I take another test? 
​Is there anything else it could be that is delaying my period? 
​Any comments would be really appreciated! Thank you