I agree with DropYourSword, giving personal opinion on timescales may be just as much pressure on the OP to not terminate as her DP is putting her under by wanting her to terminate.
I don't think the OP has asked for medical facts, but she also hasn't asked for personal opinions on timescales. Her post has never been about timescales, it's about her and her partner disagreeing on continuing the pregnancy and what to do for the best.
And I think all we can really say on that is if she doesn't want to terminate, then she shouldn't be forced to.
She does have to think very carefully about what this means for the future, for her relationship, for her other child, for her financial circumstances and for her own mental health, and make the best decision she can based on all of that.
But advising her to think carefully, to find someone she can trust to confide in, to speak to her doctor, that's as far as we can go after we've reassured her that she shouldn't feel forced into a decision one way or the other by anybody else.