Good luck to you and the baby both, keep us posted on your pregnancy :D
Guilt is a good reason to feel that way. You'd have to take a paterity test to be 100% though. BUT if the other guy wore a condom, my guess would be the one who didn't.
It sounds like Guy B that you had the unprotected sex with would be likely to be the father. Based on the LMP date you provided the following would apply:
Your next ovulation will most likely occur on Saturday, Nov-27-2010.
Your fertile days are between Wednesday, Nov-24-2010 and Monday, Nov-29-2010.
Hope this helps.