Advice please

[Crayth04]

Good afternoon I’m new to this so unsure if iv done it correctly fingers crossed I have......
So I met my Oh on the 21st April and my last period was 23rd of April but it was very short and not heavy as normal. On 23rd may I got a positive pregnancy test. I’m now currently around 14/15 weeks

I had a 9 week scan they put me 2 days infront of my dates from last period
12 weeks scan they have put me 6 day’s in front which means I wouldn’t of even met My oh at this point but I no scans can be up to 7days either way!

This has now set my mind working 5 million miles an hour

If I slept with someone on 12th April 21 days after my last period and what I thought was my period was spotting is it possible it could be his not my current partners or are the chances unlikely to ovulate so late!
Also would I be miles ahead of due date they have given me would they calculate from my month before period?

Am I just looking into everything to much and just take the scan was a little bit out help!!!