I don't know my lmp, but my due date is january 22, 2013. When did I become pregnant?

Around May 1, 2012. A woman who doesn't know her lmp (meaning she isn't sure when the first day of her last normal cycle was) or who doesn't have regular cycles nor knows how long her cycles are, can use the u/s to set a due date (good accuracy when done at 8-11 weeks gestation). She conceived (got pregnant) 38 weeks before the due date, and is called "2 weeks pregnant" or "2 weeks gestation" the day she conceived.