My Ex husband was like this. This work colleague was suddenly his best friend from absolutely no where. He was on his phone (strategically deleting messages of course), “working late”, going on work nights out when he hadn’t bothered before, picking fights with me for no reason so I was the bad guy, being short and snappy with the kids.
He denied it of course, she was just a friend, I was just jealous, didn’t I trust him?
So I ran about, trying to be the best wife, be more affectionate and loving while he looked at me with almost hatred.
I didn’t realise it at the time I was doing the “pick me” dance.
I finally caught him red handed, when I managed to sync his WhatsApp onto an old iPad and watched the messages go back and forth where it was obvious they were sleeping together. Although their chat was pretty dire, they spent most of it degrading me, how ugly I was, how my body was wrecked (my youngest was barely a year).
I went full on scorched earth that very minute. Now he’s my Ex, karma came back on her pretty hard as well.
You need to take control. I know you are afraid, I was too. Get planning on how you will survive on your own because you are on your own. Once you have a plan, you’ll find your strength to tell him to go.