"Knight in shining armour" "a perfect man to her" Sorry mate, but you're sounding a bit up yourself. I don't know if this has anything to do with the problem.
Look, any guy can give hot oil rubs and bring flowers and wine. But what about your emotional connection with her? Do you crack each other up with laughter? Do you share the same morals and ethics? Are your goals in life the same?
I noticed that you glossed over my question about your long working hours as being "sad that you do so many hours". But the question still stands: do you get enough quality time with her? Sure, a Friday night with wine sounds good - but it may not be enough to sustain the emotional connection she needs. Does she complain about not getting enough time with you?
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.