Hi, nicey, I also get April 3 or 4 for conception, along with your doctor. That is just a bit late for the guy on the 28 and 29 to be the dad.
Those ultrasounds suggest an earlier conception about April 1st, which puts the 28/29 guy in the running. It's possible you ovulated cycle day 11, three days earlier than standard, but since the ultrasounds were not very early, I am inclined to think they simply show a baby a little larger than average.
If it was the 28/29, I can visualize him ejaculating in foreplay, wiping off before he entered, but leaving enough semen in his urethra to cause pregnancy. To be absolutely certain a paternity test will be necessary. If I had to put money on it I would bet on the boyfriend.
Hi, nicey, do you have regular cycles of 28 days? If not, how long are they? And did you get an ultrasound yet? If so, when, and what did they say regarding your due date?
If you have a 28 day cycle, ovulation is most likely cycle day 14, here April 4th. Unprotected sex from 5 days before to one day after ovulation can result in pregnancy. On this basis the boyfriend could be the father, especially if you sometimes have a cycle a day or few longer than 28. He also nutted inside, which greatly increases his chances.
The March 28/29 guy has a much reduced chance since he pulled out and anyway was further away from ovulation. You don't say who you were with April 2nd. The Guiness story comes under fake news, but since he also pulled out the chances are somewhat reduced even though he was closer to ovulation.
Here's hoping it helps.