No period three days past expected period and a negative pregnancy test could i still be pregnant?

Possibly: Have you always been regular? what kind of pregnancy test did you have done? was it an over the counter home pregnancy test? Some can provide false negative results. I would recommend repeating it. If it is still negative then I would just wait a little longer and see if your period resumes. If that does not happen then it is time for you to have your doctor order a serum(blood) pregnancy test.