help

Hey can somebody help me out my period was april 12 2013 i know that forsure and my periods are usually very regular. the doctors keep saying im due january 24 2014 which would have put my period at the 19 of april and i know forsure i wasnt on my period then. But the weeks there giving me would put my due date at january 19 2014 not january 24 2014. im just confused. Is it possible that i could ahve ovulated on the 5 of may and got pregant if i had sexual intercourse on the 27 of april.