Measuring earlier than what I thought

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So I went to my first appt today. I had my “period” sept 21-28 and thought I was 7 weeks 3 days today. I went today and it turns out that I am measuring 11 weeks and 1 day. So my “period ” was actually implantation.

The weird thing is I went to the OBGYN on September 25 to discuss how I can be prepared to become pregnant and check if there were any issues. I had a pregnancy test that day and it was negative.