Husband had an emotional affair

Has anyone else dealt with this? LONG. 
Im so upset, sad and angry all at once. I am pretty sure i believe that they never were physical with each other but its still not ok. 
Basically my husband has been feeling really down about life in generAl and i guess he just needed an ear besides mine to listen to him. And honestly that isnt what bothers me. What is disturbing is that the woman he chose tk be his listening ear is a single mom that is looking for a baby daddy. Red flag number 1. She also has a reputation around my work for f-ing around with married men. Another married man that works in my department  had some what of an affair with her. They would text constantly. She would send him nudes. They would meet in the back stairwell that barely gets used and do innapropriate things. She "fell in love" woth him and then he ended it. He just wanted a fool around buddy. 
Than along comes my husband. I know the things shes texted to man nmber 1 bc he showed them to me. Thats why this is so hard tohandle. How do i know that my husband and her werent sexting or meeting in the stair well? I found a text from her and i swear i wasnt snooping but it said i love you in it.
When i questioned my hasband (i didnt know they were friends until i saw this text) he went on the defensive and then when i ran out of the house and srove away crying he was ready to explain things. 
He said originally he  just wanted someone to talk to and then this girl started developing feelings for him and he "played along" so she wouldnt tell me there was something going on.  YOU DONT TELL ANOTHER WOMAN YOU LOVE THEM EVER! 
Im so hurt and upset. I cant stop thinking about. Tbis all happend frisay night and its all i can talk about and think abut.
I feel like i did soemthingg wrong. We havnt been geting along for a while now. A few months but weve never tried to make it better. He has t put forth any effort nor have i. He told me that they talk about our relationship alot and she told him that we need to reconcile our marriage and make it work. How do you develop feelings for a married man that is "trying to make it work with his wife"? I just dont understand. And i know its not all her fault. My husband is 50 percent responsible to.
I just dont know how to cope with this. Now some bitch knows more about me than i knwo about myself. Ahe knows all lf our marital secrets. She knows everything. And i also dont and will never know the truth about hlw far this relationship actually went. 
I just am looking for someone thats dealt with this or some advice or what to do to cope and move on. I dont want a dicorce. I want things to work with my husband. Neither of us are perfect by any means. I just feel so unloved. Is it because i got older and i dont look good anymore? Bc i dont ahve time to work out anymore (we have a 4 month old) im not a fat tub of lard but i put on a few. Is it me?