Worried about dates

[Anonym0u]

My First day LMP was 8th February
My periods normally are between 23-26 cycle
Positive test on Wednesday 4th march
I had sex only on 16th-20th February and 29th only
Is it possible to get pregnant on 29th when testing positive 4 days later?
Went for ultra sound 23rd March was measured 5w 6d when I was suppose to be 6w 2d so only 3 days behind from LMP
Wasn’t with this guy so slept with someone else on the 29th now I’m going crazy thinking that it might be possible if who it is

www.calculator.net/conception-calculator.html

www.nhs.uk/common-health-questions/pregnancy/how-soon-can-i-do-a-pregnancy-test/

If testing positive 4 days after sex then you were already pregnant

No its not 29th, the pregnancy wouldve been from 16 to 20 feb.

Not possible to be + 4 days after sex so the person who you had sex with on the earlier dates is the father.