I caught my husband and best friend sexting and I am drowning

My despair is so overwhelming. My husband is the love of my life, we have been together for 13 years since I was 20. We have a beautiful six year old daughter and I just gave birth to our son nine weeks ago. My best friend of eight years and I were soul mates, and represented the most meaningful relationship I ever hoped to have with another woman. They did terrible things via their emails, and my husband kept them as trophies. Not only did he tell her every intimate private thing between us, he shared parts of himself with her that goes far beyond the sex acts they committed. And this is the worst part: he secretly took pictures of me while I showered and sent them to her. 7 weeks after I gave birth. 25 pounds heavier than my normal weight. While I was washing my hair. He is beyond apologetic and she has disappeared from the earth -we worked together, she walked in quit, left. Responded to a few of my texts and has now blocked me. My daughter is best friends with her daughters. We went to each other's family functions. I am sickened by how much I miss her. I am disgusted by my husband but love him. I am exhausted from trying to take care of our kids, and struggling to nurse our newborn. How can I go on? What do I do?