It can take a few cycles for some women to become regular again with their periods. It's certainly possible to be pregnant even with a negative result, but it can also be your cycles are still regulating. You'll have to just see what happens....wait a little longer and try another test, just wait until next month and see what happens with your period, or ask your doctor about having a blood test done.
the above post is your answer.... yes... you can be, no... its not for sure as your body may simply be irregular right now.
and take your tests in the AM when hormones are most concentrated.