I have tested for beta hcg 3 days prior to my expected date of periods and it was negative. my periods are still not started.am i pregnant?

Can wait for period: A urine pregnancy test done correctly will give a reliable result 3 weeks after sex (or when conception might have happened) or 1 week after missing a period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and therefore lead to a repeat test. If a woman has her normal regular period, then she is not pregnant, and the test is not needed yet.