Help!

[Jems142]

Hi all,
Hoping you can help me with a question I have... I have discussed before but it is something that constantly plays on my mind!
I'm 27+6 weeks pregnant (baby due 10/01/17) and I am trying to work out when I conceived.
I slept with someone on 25th March then with someone else (who is now my partner) from the 21st April onwards.
I had a period on the 9th April - 14th and I also had a negative pregnancy test at the doctors 28th April. I had an early scan that dated me 9 weeks that matched my last period on 9th April perfectly then my 12 weeks scan pushed me on 4 days so it looks like my LMP was 5th April.
Who is most likely to be the father?

[AlwaysNeverOnTime]

If your last period was at the beginning of April and your pregnancy dates match up with this, the baby must be your new partners.