What Causes Delayed Periods After Taking Injection To Prevent Pregnancy?

Hi, before i have injection prevent pregnency, but when i was with my husband blood comes out after i have my 8 days mensus, after that my mensus doesnt stop more than 2 weeks, after that doctor ask me to eat norcutin pill, i eat for 3days my blood stop and then my mensus comes out on the 8days i have my norcutin, my last mensus was on 24august and till now i havent got my mensus, its 45days delay, is it because of the injection or what??