How far along am I really?

Courtney
I've downloaded a handful of pregnancy apps since finding out - and they all range from me being 6-8 weeks. By my logic I can't be any less than 6 weeks and when I called for my first appointment they think I'm about 6 too but is there any way I can know for sure or do I just wait for my appointment on the 29th (which the waiting is killing me!)