Feeling empty and lost

I was married for 34 years, we had known each other for 3 years before that, unfortunately it ended, I ended up walking out i went to women’s refuge.
Years later I met a man on line, we got chatting, 3 years later he came to live with me, we have been together for 13 years now, we look after an old man next door, h was taken into hospital, and my partner se to go see him twice a day, when the old man came home, I noticed my partner was being secretive with his phone, and I caught him waving and smiling at someone p the road from us, I. Found out it’s a nurse that was tending to our Nextdoor neighbor in hospital, my partner is txting secretively l have approached him about it and he says he is not it’s me he loves ? I have this gut instinct that there is something going on how do I catch him out, it’s making me so sad and lonely.

Bless tell him texting another lady is not on and plan your situation if it was to end hun xx