Cancer Ex Boyfriend keeps messaging

Ok. Brief as possible but I’ll try and get all details in. Met cancer man year ago. First wife passed away, 2nd wife left him for another man. He met me (online dating) few months later. We dated. Fell for each other. Ex wife kept texting him confusing his head. We spilt up. He moved on and occasionally messaged with guilt over how he ended things. Met again, he admitted to dating two others but “they weren’t you” his words. So again, messages and confusion from him he decided not to get back together as 2nd time around he felt “no spark” his words.

I tried to move on. He certainly did as he’s now in a relationship (6 months). Yet just before Christmas he starts to text again. Apparently I’m the only one who understands him, gets him, who he can turn to blah blah. Sentimental messages of how much I was “a big part of his life and still am”. I’m confused beyond words. I cut to the chase and ask what do you want? He’s not happy. Not sure how compatible his significant other is.

Am I being an emotional crutch for him? He knows my feelings haven’t changed. He doubts what he’s done. Guilt ridden. Sentimental.

I’d have him back at the drop of a hat because we really did connect which I think is why he keeps coming back. But tell me, and I being mugged off again. We haven’t arranged to see each other. I refuse to as he has a girlfriend. I don’t message him he messages ME. I have no idea what to do. I try to move on and when I meet a new potential date, he bloody texts me. It’s like he knows !!

Need some insight into his mind set

Thanks