Emotional affair after baby!

So I have a 4 month old and after giving birth I battled with post partum. At first my husband was there for me when I needed him and he helped it alot. After she turned 2 months things got even harder for us because I was still trying to figure things out and was not able to be there for my husband. I started noticing him acting different and on his phone all the time. Come to find out he has been talking to his bosses daughter, who knows he is married btw. He fell in love with her but said he didn't want to lose his family over it. The thing is his bosses daughter is barely about to turn 18, 13 years younger than my husband and he is scared if he stops things he could lose his job. It drives me insane every day to know he is still talking to her because of it and I can't think straight. I cry almost every day I'm mad all the time I feel like I can't breath of sleep sometimes. I don't want him to lose his job because he is the one working to provide for our family. I don't know what to do!!