Hallow Dear, One of the two pregnancy tests reporting positive needs no more confirmation. Your girlfriend is pregnant. Now your dilemma is why the pregnancy test done at the doctor s office reported negative. It is likely that the first test she performed at home was on the overnight urine sample which naturally has very high concentration of hormone hCG. This is the hormone which is detected during the test. Next day, in the doctor s office, she might have collected urine sample on site which is a random sample having lower concentration of hCG in it resulting into negative result. To me this seems to be the probability. Z-Pack is an antibiotics medicine containing Azithromycin. It has no relation with pregnancy test. I hope this should resolve your dilemma. Dr. Nishikant Shrotri