Yes they thought I was 5 weeks at my first appointment but when they checked for a heartbeat and did measurements I was already 12 weeks!
My Dr actually got my dates wrong at the first ultrasound, and I knew they got it wrong cause it never marched my LMP dates and then at my 20wk scan it show that the first dates were 17 days out. I ended up moving back to my home town and got a new Dr lol
Its possible that itcould have been just bleeding and not a period at all so yes.