How should I feel when a guy I dated years ago liked me but not enough to stay with me recently tells me he still likes me.

Before I got married to my husband I was kind of “dating” this guy.. I had recently broken up with an ex of 3 years and this new boy was part of but not completely the reason for the break up. While I was in the relationship with the ex the new guy would always tell me that I need to get out of the relationship and be with him and he would call me and hang out with me all the time. Well when I finally broke up with the ex we hung out for like a week straight and everything seemed so perfect. I knew the minute I saw him that I could fall in love with him. He was just everything I wanted. But after the week of haning out and hooking up a couple times he told me in his car one night this speech “You are a beautiful girl and Ive never told any girl that she was beautiful before.. but you just got out of a serious relationship and so did I and I think we should just take one step back and just kind be more friends than anything..” So thats what we did and ended up taking like 10 steps back and not really talking at all anymore. A few months after that I ended up dating his best friend and now we are married. I love my husband with all my heart and in all honesty am glad that this boy didnt want me because then I wouldnt be where I am now, but everytime I see this boy he is flirting with me, telling me he is sorry that he met me when I was only 17 and that things couldve been differnt. I dont like him anymore but cant help thinking why he would do that to me if he liked me as much as he says he does now.. Does anyone have any advice why he would do this? Bascially I just want to know what was so wrong with me at the time that he liked me but didnt want to take things further.. why do guys have to be so confusing.. should I ask him or just leave it alone?