Hi lady_hawk and hugs of support and care to you

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I am so glad you found PC and posted about your depression and relationship concerns. Sometimes even expressing yourself as you have done here helps to relieve some of the built-up pressure within, and can give some help with working out the many mixed thoughts in your head as you try to work on a decision.
I agree with Naturefreak and Perna aabout counselling, both for yourself and joint marriage counselling, if your husband is willing. Lady_hawk, I do understand what it is like to have a husband turn to another woman, and the sense of betrayal is so very intense. It also affects one's sense of esteem, and it is natural for you to be experiencing depression with a new family and a lack of support from your husband. It is so vital that you know that his choices are not your fault, and that you need to care for and look after yourself so you are okay, and that your children are also okay. To make a decision for yourself, your children, or your marriage when you are feeling so very down is tremendously difficult, as it is hard to see yourself and your strengths clearly. And it is obvious that you have strengths or you would not have been able to seek help and express yourself so well here on the forum.
Lady_hawk, I strongly encourage you to get individual counselling so as to help yourself with your depression issues and with issues of esteem relating to how you have been treated, past and present. And I would encourage your husband to seek out marriage counselling with you if he is willing. If he is not willing, I hope you will not let his choices reflect how you see yourself, as you are a beautiful individual and his poor choices do not have anything to do with who you are as a person. I know it is hard to separate ourselves in close relationships and to not despair at times like this, but I pray you will find encouragement in Psych Central and are able to get a counsellor for added support.
With hugs of support and care for you,
BAPearl