Pregnant from precum

Okay, so I think I was ovulating sometime on september 1st.  Around 2:30 in the morning I noticed watery, stretchy cervical mucus.  This led me to believe I was ovulating.  Later that morning when I woke up, I was dry and the mucus was no longer there.  With that information I have a concern/question.  Shortly after I noticed the mucus, I had sex with my boyfriend. We used a condom, and it didnt break or anything.  This occured around 3 in the morning of September 2nd.  When we woke up later that morning around 11 we had sex again.  He started with a condom, but then took it off towards the end.  He did NOT come close to ejaculating inside me.  I know that precum can contain sperm from a previous ejaculation if the man does not urinate.  My boyfriend did not urinate after the first time we had sex so I am worried of the possibility of of sperm in precum the second time we had sex, since he took the condom off.  I guess I have a few questions. 1. How long can sperm survive in a mans urethra, without urination, and and from those that survive how likely is it that they can fertilize an egg?  2.  If he started sex with a condom on is it possible that the remaining sperm were released with the early precum in the condom?  3.  If I had already ovulated the night before and had sex in the morning, and the cervical mucus was gone, would this make it more difficult for the sperm to fertilize the egg?  I should also mention that I took plan b about 4 or 5 hours after sex that morning.  Can plan b work if you have already ovulated?  I know this is a bit confusing with a lot of questions, but I am very worried at the possibility of pregnancy.  Professional input or knowledge would be much appreciated!