My last menstrual period was on 9th May 2012, had unprotected sex with my husband on 24th, 25th and 27th of May 2012, I missed my period which was due 11th June 2012. I did not test but noticed I had very sore boobs! I had a play sex in a swimming pool with another guy on 29th June which wasn't so deep but I decided to test on 1st July 2012 and found a very dark positive line on my hpt! I am so confused I wish I had tested earlier! But could the hpt detect positive for the 2nd guy in just 3 days? Am really praying for it to be my husbands baby! My EDD by LMP is 13th feb 2013 and by ULtrasound is 18th feb 2013 taken during my anomaly scan on 27th sept 2012. I am so down and confused please help me understand. Or would a prenatal paternity test be necessary?

You have to do a DNA test after the baby is born... there is no other way to know for certain. There is an entire month window of possibility... meaning the estimated date plus or minus 2 weeks.

Ok, I will not normally go out on a limb, but if you had sex on June 29, there is no way a pregnancy test on July1st would show pregnant from this. The sperm most likely would not have even gotten all the way yet. So if you tested pregnant on July 1st, it was not from June 29.

Fr_Chuck is correct, it wouldn't show from the 29th so it would have to have been before that.

... Uhh does your husband know there was a '2nd guy'?