I Have Been On The Depo-provera Shot For Over A

I have been on the depo-provera shot for over a year, during my 3rd month before getting the shot again I was on my period for 3-4 weeks. I received the shot about a week or two late and was had unprotected sex 2 days after. It has been a week since then so it is too late to get the morning after pill. Is there a big chance that I could be pregnant?