Can conception dates be wrong? Even if they add up to my due date?
With one boyfriend we had sex everyday the 5th of December through the 18th-19th of December. I had bled a little the 11th-12th but it wasn't a lot it was spotting and not like a full period. Then got with a new partner around the 20th and so on from there.. is there any way possible that it can be the first guys? Even if my conception date is Dec 21st-Dec 29th?

Yes, there is a reasonable chance. Conception dates are estimates. Only a DNA test after birth will prove who the bio father is.

Which one is more likely to be the dad seeming how I don't know when I ovulate or not.. the conception date matches my due date.. but I'm just not sure of whose it is.. I want it to be the first guys with all my heart.. I love him. He knows it might not be his.. my due date is sep 16th and 40 weeks from that is dec 11th which is when I lightly bled but it wasn't even a full period.. I don't know what to think or to believe. On Jan 27th I found out and I was 6 weeks 3 days and everyone tells me I was really only 4 weeks 3 days cause they add two weeks but what if I ovulate earlier? Wouldn't the dates be different if I had conceived her? I just don't know :( I don't know what to do or too believe. What dates to believe or not..

It is very likely conception dates are guesses, estimates, take the date they gave you and give or take about two weeks.

So with the date given, give or take two weeks, and it could easy be.

You are too tied to a specific DATE of conception or due date, these are just average estamates

You don't know when you ovulate from month to month.
You are given a due date that is just a guess, based on just a guess of when you conceived.
The doctor bases it on the date you give her of your last period!
So if you said that it was 11th - 12th, and that wasn't a real period, and you were actually pregnant already then, then your due date will be slightly sooner (keep in mind that babies come out when they feel like it, not on some magic universal day).
So, since you want it to be the first guy, why not tell yourself it IS, because the light spotting wasn't a real period, common enough the first month of pregnancy??
But you will never REALLY know without that DNA test.

which one is more likely to be the dad seeming how i dont know when i ovulate or not.. It is impossible for us to say since your encounters were so close together.

Remember that conception dates and due dates are only a guesstimate as we have no way of knowing exactly when the sperm met the egg.

So, what it boils down to, you are going to have to have a DNA test after the baby is born.

Could it still be wrong though if I found out I was 6 weeks 3 days pregnant on the 27th of jan.. Which would mean my conception date was on christmas.. because they said count back 4 weeks three days not 6 weeks 3 days.. I feel so heartbroke and stressed about this and like nobody is taking me serious, not even my doctors.. I just don't understand even after I barely bled.. so is there any way it could still be the first guys?