What should I do if I find the news of my ex-girlfriend in my husband's mobile phone?

You must pretend you don't know this, just do what you have to do.

What you need to find out is whether they will meet again after meeting, and so on.

From now on, you should pay attention to check his mobile phone and find the secret.

So, you must pretend you don't know and don't mind.

Until there is nothing.

Until one day you found more messages.

I believe the landlord can handle himself well.