He is unhappy in his current relationship?

Anonymous
Recently I met someone at work that seemed like a charming gentleman. He frequently made subtle advances (rubbing up against me, complements that were not just casual, etc). I learned he had a girlfriend so I kept my distance. He constantly told me about how he was unhappy in his relationship. I asked him "If you were not in a relationship, would you consider going out with me" and he said he would. He told me a specific day that he was going to end it with her. However, he failed to do so. It went way beyond flirtation and he knew that I had developed an unbelievable attraction (emotional and physical) to him. I know that people say not to get involved or attracted to people at work but this was in no way planned or predicted. He still complains about his relationship and unhappiness. My friends and family tell me to just let him go because he is a womanizer that preys on women just to stroke his ego. Regardless, he still has me like putty in his hand and despite my best efforts I have not been able to forget how happy I was when he and I talked and he cheered me up when I thought that we still had a chance at something more. I know that I would treat him like a king and make him happier than he could ever imagine. I am almost a decade younger than him and I am willing to accept any faults and idiosyncrasies he may have. He may be a womanizer and may have a short attention span but he hit me deep down in my heart and I live every day thinking about him and wishing I could just have a chance with him. Assuming that he is indeed unhappy in his current relationship, what could I do to show him (without saying it, since that has failed to work and only gives him his cake and allows him to eat it too, keeping his girlfriend and having me salivate all over him), that we really could be happy and get him to drop the dead weight that he is with now and give me a chance?
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Yes; unfortunately I have heard of men lying to get what they want, and that is what my family and friends keep telling me. Unfortunately for me, my heart isn't listening to my mind and it is driving me insane. Just an occasional encounter (walking past him, seeing him uniform which is unmistakable or the truck he drives, hearing his name or smelling his cologne) brings me to tears. I am in way over my head. Figuratively, I am in a lake and don't know how to swim.
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I write poems (for my own use) about him every day and yearn to hear his voice even though I know he was being a jerk, it doesn't change a thing.
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It's like Dolly Parton's song "Here you come again" and Dionne Warwick's "Heartbreaker" rolled into one. Thanks for the advice though
He is unhappy in his current relationship?
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