My period is 2 weeks late, & negative pregnancy test, why?

It could be a number of things. You mention that you have been traveling. Perhaps the time zone changes have thrown off your body clock. Or you could be physically stressed which could cause some disturbance in your cycle. Or you could be in the process of a miscarriage- that is, your hCG levels have fallen and can not be detected on a home pregnancy test. If that's the case, you might expect some blood soon. A blood test for pregnancy will be more accurate than a home test. Since you're concerned about an ectopic pregnancy, you should go to a doctor or clinic right away and get a blood test.