For simplicity in asking you, I'll just use the term "8 weeks plus" to cover your ultrasound technician's date range of "8 weeks 1 day to 8 weeks 5 days." Please bear with me, because it sounds kind of complicated when I type it out. So --
Did you ask her specifically when you might have conceived, or did you ask her "how far along" you were? These questions will get two different answers from a medical person. This is because pregnancy is dated by doctors as beginning on the first day of your previous period, not on the day of conception. If you did not specifically ask her what your conception date was, it is most probable that she told you your pregnancy status based on the medical way to date a pregnancy. All medical charts, graphs, ultrasound comparisons to other embryos, and books are calibrated to that kind of dating, which begins on the first day of the mother's last period.
If, on June 15th, the doctor or ultrasound tech told you that you were 8-weeks-plus "pregnant," unless she knew you were specifically interested in understanding who the father is, she would date it the medical way. That means she was telling you the presumed first day of your last period was 8-weeks-plus ago. If the first day of someone's previous period was 8 weeks ago, the average person would have conceived about 6 weeks ago. (In your case, 6 weeks 1 day to 6 weeks 5 days prior to June 15).
The reason I ask is because you didn't sound like you were using that kind of counting when you said "when i went in for my first ultrasound i wud hav been exatly one month if it is my ex-boyfriends child." If the ultrasound was June 15, and the sex with the ex-boyfriend was May 18, that is not 'exatly one month' pregnant for the purposes of whether or not you can see a heartbeat on an ultrasound. Yes, it is one month from conception, but is in fact 6 weeks pregnant for all medical purposes, including comparative ultrasounds. At 6 weeks pregnant (counted the medical way), yes, you can see the embryo and a heartbeat on an ultrasound.
In any case, if you were 8w1d to 8w5d (counted the medical way) on June 15, conception would most likely have been the 3rd, 2nd or 1st of May or April 30 or 29. The gap between the possibility of your boyfriend being the dad and the ex being the dad would be about 2 1/2 weeks, not a "whole month."
If you did ask her specifically about the conception date and she said it was 8 weeks ago, then your boyfriend is the main candidate. (Unless you slept with someone else right before April 19. Then he would also be a candidate.)
If what I'm writing is really unclear, take the due date the doctor gave you on the first ultrasound visit (when you were told you were 8-weeks-plus pregnant -- that one will be more accurate than a later ultrasound) and key it in on an online conception calculator. It should help you get a good idea of when you might have conceived.
ok maybe i shud hav been a little more specific:
april 19th- last period
april 19th- slept with boyfriend until
may 18th- slept with ex boyfriend
june 15th- first ultrasound 8 weeks 1day - 8 weeks 5days
sept 17th- second ultrasound 21 weeks 5 days
what i am trying to figure out is, i no for a fact that it wud only be possible for me to be a month pregnant if i where to hav concieved on the day i slept with my ex... so i am trying to figure out if it is at all possible to see a heartbeat at exactly 4 weeks?? or is it possible for a transvaginal ultrasound to be off by a whole month?? im tryin to figure out if the dad is my boyfriend or my ex?
OK, please read again -- if you had gotten pregnant by your ex, you would not have been "a month pregnant" on June 15, the way pregnancy is dated by the medical profession. You would have been "6 weeks pregnant" by the way a doctor would date your pregnancy, since medical counting of pregnancy begins on the first day of your last period. At 6 weeks, it is possible to see a heartbeat.
However, the doctor said you were 8+ weeks pregnant. So it is less likely to be the ex's, since the doctor would have said you were 6+ weeks pregnant if so.
you should of conceived around may 6th. so goin with that I would say ur boyfriend is the father.
I think it is most probable ur boyfriend is the father