Conception dates first few days in nov?

I had a last menstr period oct 21. My periods have been 25/27 days my whole life. My first ultrasound was dec 12 saying I was seven weeks two days. all making conception first few days n nov.I went on to have six ultrasounds all backing up to 10/21 10/22. Makng conception dates nov 3_5..given those dates and lmp. Is there anyway I could have concieved on or after nov 15.