My period is 8 weeks late and i've had 2 negative pregnancy test. what could be wrong.?

Lots o possibilities: If your periods are always irregular, then this is just part of the pattern. You should not go longer than about 10 weeks without a period because the lining of the uterus can build up and get too thick, causing a really heavy period and even can lead to cancer. There are many possible causes for irregular cycles. See your doctor to figure this out.