How Safe Is Qlaira?

Hello !!I had started taken Qlaira since March and I don't have any period for two months!I did a test and I am not pregrant.As soon as I stopped them i had period.Are they too strong for me?I used to take Jasmin pills and was perfect for me,but because I am 38 yrs old my doctor adviced me to stop them!!!Why are they so "strong"'???