There are many reasons you might miss a period. Simple things such as stress or exercising too much can cause a missed period and many girls are irregular during the first few years of menstruating. But if you've missed a few periods, be sure to see your healthcare provider.
Courts usually find probable cause when there is a reasonable basis for believing that a crime may have been committed (for an arrest) or when evidence of the crime is present in the place to be searched (for a search).
Neither the Fourth Amendment nor the federal statutory provisions relevant to the area define ''probable cause;'' the definition is entirely a judicial construct. An applicant for a warrant must present to the magistrate facts sufficient to enable the officer himself to make a determination of probable cause.