More likely the guy from April than from March, depending on how reliable the source of your due date is. Did you get the due date from an ultrasound or just from counting forward from the first day of your last period on a calendar or little cardboard wheel? How early in the pregnancy were you when you had the ultrasound that gave you the due date (if you did get the due date that way)?
I got it from the ultrasound and I didn't know I was pregnant until I was 20 weeks..thats when I had the ultrasound done
Hmm. Well, some babies develop at different rates than average, some more slowly and some more quickly, meaning that an early ultrasound would have a very small margin for error when trying to decide when the baby was conceived, but a later ultrasound could have a larger margin for error if the baby was not growing in line with "averages." If you had an ultrasound at 7 weeks, it would be possible to say that with only perhaps a day or two for a margin for error, when the baby was probably conceived. But by the time you have this baby at 40 weeks, trying to decide when conception was just by measuring with an ultrasound, the margin for error is +/- 3 weeks. Perhaps at 20 weeks the margin for error would be about +/- 10-12 days.
If you put your due date into a conception calculator, it says you probably conceived around April 11. Even if we compute in the margin for error, it doesn't take you all the way back to March 18 and 19. So I would still think it is the second guy.
It would be wise to get a DNA test done when the baby is born, just to make sure of all of this, but in your shoes I would go through the pregnancy confident that you got pregnant from the sex with the guy in April.
Thanks for all your help!