Husband talking to another woman

What you you do if you saw messages from your husband and another woman flirting? She says she lives in NJ which is on the other side of the country but they are being flirting with each other and been talking to each other multiple times a day since last Friday. What would yall do? He has never done this before and he has been stressed out lately with us having a 2 year old and another one on the way, school, be coming a citizen and trying to fine another job.