Can Folinine Tablet Helps To Get Period?

doctor i have irregular periods problem.then i consult a doctor she gave me some medicines then first month i get periods 4 days late, next month 7 days late, now it takes too much time 18 days still i am not get periods.then i take pregnancy test but it gave negative result.2 days back i consult my doctor then she doubted that i have pregnancy and recomended me folinine tablets for 10 days.she said come again after 10 days. am i pregnant now? then why the test shows -ve result? folinine tablets r they work on me?