hi iam wondering if you can help me iam goin crazy i need to know who the father of my unborn baby is!

my last period was on the 4th of september 2010

i had sex with guy 1 on day 7 of my cycle and had sex with my husband on day 9 of my cycle, i ovulated on on the 17th of septemeber reaseon why i know this because i was bleeding only for 2 hours!

my 1st ever scan was october 28th and nurses said i was 5 weeks and 5 days. the most recent scan i have had is 4 days out from this one iam confussed can u please help me. i think iam 31 weeks in 4 days time