It sounds like a complicated relationship. Welcome to this site. There are others here with experience similar to yours.
A few things come to mind. First, just because your kids say they treat their stepmother better than they treat you, doesn't mean it's true. Can you get on the phone with her and compare notes?
Also, when they say this, ask them calmly why that would be the case. Why are they so angry with you, that they have to make an effort to hurt you? And where did they learn such unpleasant behaviour? Ask them. See what they say. do try to not argue with them about it, because you want honesty from them, you do not want to reward their honesty with your disapproval.
How come their dad has custody? Is there something that happened that your kids may blame you for? Or something that was said to give them a bad opinion of you? Whether it was done or not, whether it was true or not, their belief in what has been happening is what you need to determine, and you need to disprove. Not with logic, but with your example to them. A number of options then arise, depending on what the answers are.
What about your current husband? How is he with all this? What is his relationship with them like?
Marg
