Hi,pregnancy test will become positive usually 7-15days after missing periods.. ur periods is already delayed by 25 days and still no sign of period .. u can repeat a pregnancy test.. if negative then need to consult a gynaecologist .. they will suggest you medications for getting periods after doing necessary tests.folvite tablets will not change the pregnancy test... it is usually taken as prenatal vitamin when women is planning for pregnancy.it will not cause any harm..