I had a Kenalog shot for the first time at the end of october for...

I had a Kenalog shot for the first time at the end of october for sinus infection. My menstrual cycle for November lasted 20 days and now for december it is the same thing. I have bleeding for 4-5 days and then it stops for a day or two and then comes back full force for another 4-5 days it seems like I had three full cycles this month? My doctor says that it is not from the shot but for over 25 years it was regular 28-30 days? What is going on and when will this stop?