Unsure how far long I am

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Based on my last period (5th September) I should be 6 weeks today but I didn’t get a peak ovulation test till the 27th of September. When I called to make my initial booking in appointment I explained the above they said they would date it from my last period at the moment. However, it’s killing me not knowing how far along I actually am! I had a chemical pregnancy in the past as well so I am finding it so hard to not feel anxious that something might go wrong. I am in the UK so have booked an early scan for next week but otherwise wouldn’t get my scan till 12 weeks!