Step Families Support Group
Traditionally, a stepfamily is the family one acquires when a parent enters a new marriage, whether the parent was widowed or divorced. This community is focused on many of the relationships and issues that may arise within stepfamilies where you may find answers from some members and you may help other members with their questions.

Although, as long as there is love there and he is supportive of you, it has rewards. I think with the kids, they are constantly changing. One moment they will be great, the next you just want them gone. How old are his kids?
At any rate, I am sure it beats your abusive relationship. Nobody deserves to be in a situation like that. Are there plans for marriage?
One good thing is that the kids are young still. And if you can stick it out you have a good change of making a huge positive in their lives. If the ex causes drama for your family, my guess is her drama is something she thrives on and as the children get older they will gravitate towards you and your positive ways.
There is the possibility that the pregnancy is a huge part of the emotions your having. And from my experience most fathers are going to be defensive when it comes to their kids.
As far as the health issue.....well that can be so frustrating. I am sorry that the ex has no compassion for your household and doesn't take good care of the kids health.
If you don't mind me asking. What is the parenting plan between the mother and father? Do you have regular visitations? Is he custodial or is she?
Try and keep your head up, I am certain with time everything will look up.
It would be the nice and polite thing, since, you are in her children's lives. I don't regret doing it because I know I did try. That has to be something you really want to do. Ask your fiance for help with that one.