Dating Help

Hi, my last period ended on 19 September 2017.

I did not have a period at all in October I had a slight brown smudge when whipping once but nothing else at all. ( I am normally a million % regular 28-30 day cycle- I have never missed a period)

Did a test today got a strong positive but clear blue digital says “Pregnant 1-2” but given my dates I would have said 7 weeks?

What would people go off test or period dates ??