Last month period was March 1 period is anywhere from 28-30 days. Currently pregnant and my due date has been changed 5 times it was first 12/6 then it was 12/13 then 12/15 back to 12/6 now they are saying 12/21 because she's measuring small. Weighs big for how many weeks I am but measures small. If 12/21 is my new due date than means I didn't conceive until a week after I got my positive pregnancy test. Makes absolutely no sense. When do you think I conceived?