We don't know if he is the father since we
do not know your sexual history. A DNA
test could always be performed at some
point if you are unsure.
There are a couple of ways to determine
how far along a woman is.
"Pregnancy can be dated from the first day
of the last menstrual period or it can be
dated from the day of ovulation.
In the United States, pregnancy is dated
from the first day of the last menstrual
period.....According to this system,
conception doesn’t actually occur until
2 weeks of pregnancy....In many other
places, the new knowledge has been
incorporated into a dating system that
starts with conception. In that system,
pregnancy starts on the day of ovulation
(usually the day of conception) and lasts
for 266 days (38 weeks).
In both systems, the due date is exactly
the same. It only makes a difference in
calculating how far along you are during a
pregnancy. For example, in the American
system, the first trimester ends at
approximately week 12, whereas in the
other system, the first trimester ends at
approximately week 10. The following table
illustrates the differences:
Event American System Ovulation system
Conception Week 2 Week 0
Positive pregnancy test Week 4 Week 2
End 1st trimester Week 12-13 Weeks
10-11
End 2nd trimester Week 26 Week 24
Due date Week 40 Week 38
Similarly, if you are trying to calculate
backward to figure out when you conceived,
you need to know what system your doctor
used when calculating your dates. In the
American system, if you are 7 weeks
pregnant, you conceived only 5 weeks
ago."
http://www.askdramy.com/dati
ng.html
