Anxious about dates please help

I had an early scan on the 6th dec and I measure 5+4 weeks. The problem is I made a one off mistake on the 15th September is this date too far fetched or am I being paronoid. If its not the 15th then it is my regular bf. I have my "12" week scan tomorrow I am jut so an anxious with this date

[vico75005]

Ill say 15th of sept too far along...

[eggywegg]

They are pretty accurate when they say how far along you are. If they said 5 weeks, they are probably right.  Also- if you are alone with the sonogram person you can just ask if there is any way it could've happened on the 15th and see what they say. That might help put your mind at ease. Good luck.