The first date of my last period was 06-22-09, but my period was extremely light. My periods aren't regular so I cant give the # of days in my cycle.

Here's my problem- I had sex with a friend on June 24, 2009, then with my boyfriend on July 5th and thereafter. I had my first ultrasound on August 11th, that said I was 6 weeks along. I just got a second ultrasound on 9/23, that said I was 13 weeks, 3 days along- which is 8 days longer than previously thought. So, my question is, is there any possible way that my friend could be the father of my baby?? Im really going crazy, any advice would be helpful!

Thanks!