Date of conception ..

Momofboys • mom of 3 on earth and twins in heaven.. due 4/28/17 after 13 months of infertility..
I'm just curious when my date of conception was. I had a mc the week of July 30-August 4, stopped bleeding the 6-7th. Took a blood hcg on aug 26th it was 4.89, took a hpt sept 2 got my first bfp. Had hcg levels done sept 6th it was 137, sept 8th 537, sept 10th 1567. Due date is May 12, 2015.. I don't kno when I ovulated..