All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
First of all, we ask Allaah to make a way out for you from difficulty, facilitate your affairs and reconcile between you and your husband, as He is the All-Hearer and Responsive [He accepts the supplications].
You should know that your husband has the right to prevent you from speaking to your ex-husband or sending him messages and the like, and you are obliged to obey him in this matter because a woman is obliged to obey her husband within what is permissible. The Prophet said: "If I were to order someone to prostrate to other than Allaah, I would have ordered the wives to prostrate to their husbands because of the great right that Allaah made due to them from their wives." [Abu Daawood] However, your husband should accept your apology for breaking your promise to him for not corresponding with your ex-husband especially that you did so unintentionally.
As regards him being determined to divorce you, then this is clearly wrong because you did not do what necessitates divorce. Therefore, it is more appropriate that your husband understands your situation and sees the reality as it is without magnifying it. Furthermore, you should know that your ex-husband has the right to see his children even if they are in your custody. Indeed, the jurists agreed that each parent has the right to see his or her children if it is the other partner who has the right of fostering them.
Therefore, you should have a mutual understanding with your husband so that both aforementioned matters will be achieved. So, you may seek the help of some pious and righteous people so that they would reconcile between you and your husband so as this mutual understanding would take place.
We think that the solution is easy because it is possible for the father of the two children to see them in the presence of your husband, and you may send any message to their father through your husband regarding any matter of theirs, among other solutions by which the objective can be achieved without any suspicion or dispute.
Allaah Knows best.