How exactly do you know the set week & day of how far along you dare?

Mo
Hi there, first month TTC, but lots of research along the way. I've had about 7 BFP since last Thursday. And I'm telling my husband tonight :)
How exactly do you know how far along you are? Last period start date was July 26. My fertility window was August 4 thru the 9. There was a lot of trying going on during that timeframe, so idk what day we conceived?
Last week (Thursday thru Saturday) the ClearBlue said 1-2 weeks, and on Sunday the test said 2-3 weeks. Can someone help me figure out the most accurate week & day?