My husband left the kids and I

So we have been having issues in the marriage, and he suffers from mental illness. I found out over a week ago he had been talking to a 20 year old girl at work. I confronted him with this, we argued, then he said he wanted to work on the marriage. Two days ago he said a job came up and I blindly believed him. I waited all day, the whole time he was texting me he loved me and all these details about the job. We were supposed to go get our crib for when the baby comes, he never came back. My 41 year old husband left the 2 kid's and me for a 20 year old. Now what