Positive after 16 dpo

Well I have 3 beautiful girls, and with them I had always got positive pregnancy test at 9 or 10 dpo. For me even though I have seen a lot of people getting positive after missed period, I thought I was the kind of person that shows early on a test. So I was ttc for 8 months and no luck. This month we did the deed and because I didn’t test positive from 8 dpo to 15 dpo. I thought I was out. Well I had 5 days late and just today I have a clear positive. Omg what a surprise because like I said I thought it was not possible for me.