How do I get the girl I casually dated to forgive me and take me back after I broke up because I tried to reconcile with exwife?

I (40M) was married to my ex wife (40F) for 17 years, divorced 3 years ago. The divorce was largely due to incompatibility and lack of intimacy. She hurt me deeply with several comments that stuck with me. Bad in bed, don't last long, not enough for her sexually size wise. Divorce and my bad in bed report card screwed with my head, I couldn't date anyone out of fear of disappointing anither woman when my friends set me up

After divorce i went on a trip to England, saw a former coworker, we decided to catch up. It wasn’t serious, but it she was incredible and helped rebuild my confidence after my marriage ended. The day we were just catching up, she was flirting with me and I even thought, there's no way, she's gorgeous. She noticed, probed, and was so warm and understanding. I explained what my wife said, she being more experienced explained to me basics of sex. I had no idea men last longer 2nd or 3rd time around, or that women need other form of stimulation. Ill never forget what she said about the "size issue" , "how about i investigate and report back".

I couldn't believe how quickly I developed longing for her and kept flying back and forth to her for months. for many years all I wanted was intimacy in my marriage, and finally this woman showed me what its supposed to feel like. I felt with her direction, I even got good and confident in bed, it was incredible.

Ex wife and I are generally civil, but about 2 months back she suggested reconciling. For cultural and family reasons (we share a child and are both Punjabi), I felt it might be worth exploring, maybe there is something left after 17 years.

I ended things respectfully with the woman I was dating and focused on seeing whether my ex and I could rebuild something. The minute I got off the call when I ended it with the woman, I felt I made a huge mistake. She seemed understanding, I wish I did it in person considering how incredible she was to me.

It’s been about six weeks. While things are better with ex wife, she is trying and she was surprised at how much better our sex life improved, she now told me she wants to remarry. I realized its a no for me because I can't stop thinking about the woman I dated. I miss how natural and passionate things felt with her. I know it wasn’t love yet, likely infatuation and I also understand she may not want anything serious, especially after I chose to try again with my ex.

I'm ending things with my ex again, its not fair to her i keep thinking about this woman.

Would it be inappropriate to reach out to the woman I dated?

Or is that unfair to her? I’m trying to figure out if I’m chasing something real. I think about her daily. I understand this might mean I'll end up with no one. I came to terms.

Tl;DR: I reconciled with ex wife of 17 years only to realize I miss the girl I dated after our divorce, ex and I can never work out. Is it wrong to ask her to take me back, even if it can never lead to a full relationship.