The only way to definitely know who fathered your child is if you only had sex with one person or you had sex with several men at least two weeks apart. You had sex with them too closely together to know with certainty which one fathered your child. You'll have to take a DNA test.

i'm having an early scan tomorrow. will they not be able to look at the size of the gestation sac to determine.

It will be pretty close but not exact. Ultrasounds can be off by 1-2 weeks.

i would say guy B. it seems more plausible. but the ultrasound will definitely help determine that.

i had an ultrasound today which showed the gestation and yolk sac measuring 10mm x 4.1mm showing that i am 5 weeks pregnant. i then had an appointment with my midwife and doctor who said that that must mean that i fell pregnant on 28/29th april even tho my lmp was 11th april. i ovulate quite late in my cycle which is good news for me as i accidently had sex with another guy (a)right at the begining of my cycle and was a bit worried the baby could be his but now this has confirmed that its not and is def guy b's. i'm so happy