I am now 8 days late for my period. I have a fairly regular cycle and have never been this late. But I've taken 3 tests now and they all come back negative. Could pregnancy be a possibility?

Sure it's a possibility... but at only 8 days late you are taking the test too early... false negatives are much more likely taken before you are 14 days late... and some women will test negative much further into their pregnancy.

I'd suggest waiting another week and retesting... first thing in the AM, right after you wake up... the first time you pee that morning.

As well take a look at your life and what could be changing your cycle. Stress is a obvious one, but there are other things like illness and drugs that could be delaying your period. Maybe just a off month.