I administered a Shot of Ovidrel on Saturday 7/14/08 day (17) of my cycle. Today 7/19/08 is day (22) of my cycle, I normally get my period on day (26), so I did a pregnancy test and it was positive. How do I know if this is a false positive? I read in the information for the pregnancy test that Pregnyl and Profasi give false positives but does Ovidrel also cause that? How long does Ovidrel last in your system?