Tons of negative test results? could i still be pregnant?

My older sister could not come up positive on a HPT till after she was three moths pregnant, and two weeks ago she gave birth to my beautiful healthy neice! Some women develope the HCG hormone slower then others, or develope the other hormones more then the HCG which could be deluting the tests. If your period doesn't show up here soon make a doctors appt for a blood tests. These seem to be much more accurate with very little fail! Lots of baby dust:)