What you are saying, "I'm a good mom!" and "I just WANT them!" are both all about you. From just the little bit you've told us, whether you are a good mom or not is somewhat questionable. You certainly do not sound like you've at any time put your girls needs anywhere above your own wants and what seemed easier at the time, not to mention reproducing with another new dad and giving yourself another huge responsibility when you aren't able to support that new child any more successfully than you have been supporting your other two children. They can very easily figure out what your priorities are.
If I were their father, I'd be frantic in my efforts trying to get them back with the parent who at least has car, money, place to live, you know, a few of the basics for successful parenting. You flew the coop because your ex's family was harassing you, possibly noticing what a poor parent you were, questioning that?
Any court in the land will see the custody thing this way. Your daughters need parents who can take care of them in all ways. They need someone who makes them a priority. Not someone who flew away on a whim, has just a new boyfriend with a baby due in June. And there's a very good possibility that this relationship won't be the replacement for a more successful life that you need to be working on to retain custody of your two older girls. If you want custody, get an attorney, which means, of course that you'd need to have this new baby, get a stable place to live, some form of supporting yourself and these children, and a way to show the courts you COULD be a good mother.