Stressed to the max

[NancySmith01]

I really hope I'm writing to a real person / OBGYN
I had a doctor appointment on 06/16/16 , 2 weeks after a positive pregnancy test . I don't remember my last marking period so I couldn't use that . I had an ultrasound that day and measured 6 weeks & 3 days.
Now here what has been really stressing me out . On 05/02/16 I had an intercourse with an ex , he used a condom . On 05/05/16 , I had an intercourse with a different partner . I don't really trust in condoms and I know they're not 100% but is killing me that the first partner may be the father .. I don't want that . And this pregnancy has been very stressful for this reason

[AnnieBrooke]

Hi, Nancy, the real question is who you slept with closest to May 16.  You were given the "weeks pregnant" or Gestational Age by a medical person.  If a doctor, nurse, or any medical person says you're 6 weeks "pregnant", it is not a figure that counts back to conception but to two weeks before conception, to the first day of your last period.  All medical counts of pregnancy (the number like 6 weeks 3 days or 11 weeks 4 days) begin two weeks before conception in order to line things up with the assumed first day of the woman's last period.  If a doctor says to a woman, "Congratulations, you are 6 weeks pregnant!" he means 6 weeks since her last period began and about 4 weeks since conception.  

The count is done this way because the period is a big, obvious signal, not because the doctor thinks you are pregnant when you are on day 1 of your cycle.  (The doctor knows you were not pregnant then -- you were having a period!)  But that is why pregnancy, which takes 38 weeks, is counted as being 40 weeks long.  They add a spare two weeks at the front to be able to calibrate the count to the presumed first day of the last period.

So, don't spend a lot of time trying to decide between a guy with whom you had sex on May 2 and one with whom you had sex on May 5, look to around May 16.  It would not be the guy from May 2 unless you had sex with him later.