I have a question (and it's probably silly), but it always confuses me.

When you say that you're "six weeks" pregnant or "twelve weeks" or what-have-you, is that the weeks since your last period? Or is from when you actually conceived?

For example, my last period started March 4th and I O'd on March 19th. If I were to be pregnant now, would I say that I'm two weeks pregnant?

Just curious how that works!