Me,
What your spouse did was to endanger you and endanger your unborn child. This is not a man who has your best interests or those of his family at heart. If you give some thought to the fact that his hookups were more important to him that your health and the health and welfare of his children you will see that you have nothing to work with in your marriage, and that in order to save your children from growing up in and then reproducing in their own families the dysfunction and selfishness being modeled to them and disrupting the peace of your home, the choice becomes not "if" but "how and when." You don't stay for the children; you leave for them. You model sanity and responsibility to them. Yes, it's scary. But it's also scary to contemplate what other STD your husband might bring home with him next. HIV?
You're in a very tough spot. Places you can seek help are these: your pastor (if you belong to a church), your parents or siblings, a women's shelter, your doctor, and a lawyer, who can help you understand your legal rights, and the type of support your husband will be required to provide for you and your children.