Well, you can figure out and estimated due date based on when you might have conceived but if you got pregnant before you got a period after getting off the BC I don't know if there would be any way to know until you get your first ultrasound. Congrats mama!
Anyway, think about the days in that two weeks that you had sex, use any one of them and go online, google due date estimators and you should be able to find something where you can enter the date of conception and it gives you a guess of when you might be due.
You probably ovulated at the same time you had your IUD out. I would calculate your due date as April 19th, 2013 based on that. Congratulations!