How far along am I?

Question

Ok. So I'm confused. I hope someone can help me.

I got a positive pregnancy test last Thursday (Sept 3)- 3 days before my missed period. 
Today I went to the health department and they said based on my last period (started August 13) I am due May 21. Which makes me just over 3 weeks pregnant. My last period was definitely different than normal. 
I have not seen a dr yet, but my question is this. Could I have gotten a positive pregnancy test a week ago (when I would have been, according to the HD only like 2 weeks pregnant) or am I farther along than they said. 
Also, I had been having pregnancy symptoms for at least a week or more before I got the positive test.

Any input is appreciated. Thanks!

Answer

My periods are super regular. I have about a 23-24 day cycle. I had some rather strong cramping on August 26.

Answer

I have irregular periods as well, and can't count the date of my last period toward  gestational age as I ovulated late. According to my last period, I am over 5 weeks along. In reality, I'm 4 weeks. I got my bfp at 3 weeks 4 days.

Answer

I determined mine by the date of conception bc I have irregular periods and I ovulate earlier than day 14.  My last period started August 9 which gives me a DD May 15.  But I either conceived in August 18 or 20.  I chose 20 bc it was later.  So that makes me 5 weeks today.  I have an appointment Monday to confirm.

I hope that helps!

How far along am I?

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