@Heartbrokenpoppy very similar happened to me. I caught him on an adult site that has sex workers. He had messaged one and was arranging to meet her. He even sent a follow up message to let her know his travel plans had changed. When confronted, I wanted to know why he was meeting sex workers when he had a GF at home willing to give him all the sex he wanted and his pathetic excuse was worse - he didn't realise he'd have to pay. He thought it was a real person looking for a casual hook up. I even laughed at his idiocy because he'd gone on an overnight away for work with £30 in his pocket (we were skint) and would have had a shock when she showed up demanding payment and that is all he had.
I loved him so much that I let it go. I let myself believe it was a one off moment of stupidity. A month later he fell asleep on the sofa with his phone in his hand, unlocked and there was a dating website up where he'd been looking at a particular girls profile - this was Valentine's Day BTW.
At that point, my shock and pain from the first time transformed into anger and I realised that no matter how much I loved him, he did not love me back.
I then understood my own self worth and despite the pain, I dumped him and stopped speaking to him. I removed all his access to me.
Rip the plaster off the wound, @Heartbrokenpoppy . No second chances because if his eye is wandering now, he is already emotionally disconnected from you and the love is gone leaving a residual affection and fear of being alone.
You are worth so much more than that and you deserve better. 🌹