Is Tiredness, Nausea And Headache A Sign Of Pregnancy?

Hello... I have a question regarding pregnancy.

A week ago was the last time my girlfriend and I did it. Now don't be so quick to judge, as any teen would try to last longer. Before we got down, she gave me a hand job so I would last longer. To avoid making any messes while ejaculating, I covered it with my underwear. Well, I went to the bathroom, wiped it off, and went back to her room. As I went to go put on the condom her parents came home. At this point the condom was on, I was at attention when we paused to let her parents leave quickly.

I am worried because during that brief period I believe the condom could have possibly come into contact with sperm that was still on the underwear. I had wiped it off, but If any sperm from a previous ejaculation came into contact with the outside of the condom, could she be pregnant, or would the sperm have died in that brief "5 minute" period?

Also, it's been a week and she gets very tired and nauseous at night along with tiny little headaches. She says she ate too much, but only being a week in do you think she could be pregnant?

Thank you for any input you have to offer!