don't care your husband anymore, take good care of your baby and yourself first. If you are not happy, your baby will feel it too. Whether you decide, always put you and your baby's happiness first, no matter what your husband said to you.
i'm glad that you are strong and decisive about your future instead of keep letting him to drag or tortune your life. Since you are still young, go get a job and put the baby in the nursey or hire a helper. If he has a bit mercy, ask him to pay for child-support. If I were u, I won't spend time to think about their relationship anymore, it is not about the other woman, it is about your selfish husband who wants to have affair and a marriage at the same time. It is an nonsense that he said he loves u. How can he said he still loves and cares for u and the baby and your family if he has affair with other woman.
Good luck to you ! Don't cry too much as it is not good for your health! Take care!