It's from the day of your last period ... that's all I'm going by because I haven't had any scans yet.

So my last period was on a Saturday - so every Saturday my week changes. Today I am 9 weeks.

There are various pregnancy calculators on the web - just do a Google search. Or even go to a ticker website and get a pregnancy ticker. You will just have to put in the date of your last period and then you'll have your countdown.