Hi, we've been into this already in depth. Perhaps you could talk to a counselor about the guilt, because obviously everything everyone is saying to you on this site is not helping.
So talk to your doctor,maybe it'll relax your mind and let you enjoy the last days of your pregnancy.
Its easier said than done, but don't let it consume you. .. what ever is going to happen, well it's just going to happen and stessing your self won't change this.
Anywho
A woman with a average 28 day cycle conceives 2 weeks (10-14 days after lmp )
Example. Lets just say a woman has a period January 17th. Has sex with guy A on January 26th. But... starts her period Feb 18th. Guy A isn't the father.
Then she has sex March 1st, with guy B doesn't start her period March 17th, ending in positive test. Guy B is the father
But, if she had sex with guy A & B only a few weeks apart, in the same cycle, only a DNA test would be able to tell
A woman's egg only survives 24 hours while a males sperm can survive up to 7 days waiting for a egg. So with in a two week period with in the same cycle, both males sperm can still be up there waiting. When in fact only one is successful.
Hope this helps & good luck!!!