Can I be responsible for that pregnancy

can I be responsible for that pregnancy ? I traveled
for 5 months without seeing my gf. when I came
back I had sex with my gf she called to tell me she
had missed her period a week afterwards. we went
for ultrasound scan on the 12 day after we had had
sex and we were told her pregnancy was 4 weeks
old. she cried it can't be true we took another scan
the same day and it was 6 weeks. she says
because the results vary she dont trust it, beside
am the only person she had slept with. my question
is can a scan detect 12 days pregnancy?
Asked Feb 19, 2014

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