help with due date ..

Stacey • 20 year old with daughter at 4:), pregnant with #2

When I went for my first scan on the 25th July they only saw sac and they measured it and says I was 5 wks 5 days so I should be now 7 weeks today, got another scan on the 8th August. Should I find out my due date then I know it's around 22nd march 2015, on Friday the 8th August I will be 7 weeks 5 days ?  X