Take note that normal pregnancies are actually technically 10 months long. If you guys were just dating 20 months ago & not official, no harm no foul..but he should've told you sooner, how can he be in his daughters life without you noticing? get rid of him for that..

Obviously he's been cheating on you, has not been completely honest with you or both. Both are red flags in any relationship.

#89 Math people... MATH... A person is 29 years 8 months and 2 days old. Do they say that? No. They say they are 29. 2 years -1 year -9 months =3 months The daughter just has to be a minimum of 1 year and 3 months to not be the result of cheating. Then add months for each month over 2 years the relationship was. even still, there is a chance, although not high, that the boyfriend had this daughter with the previous girlfriend, impregnating the child's mother right before the break up.

But with that logic, realize also that the daughter could be one year and some change. So it's still possible that it wasn't cheating. That said, it is an FML, so it's kind of a safe assumption that it was.

This really needs a follow up

If you are sure she was conceived after the two of you were together, then it is definitely not cool. Just be sure of the timing first.