I look back in embarassement

I dated this person 4 years ago and only for 3 months! One of which I was in a different country. I came back home, he broke up with me due to an evening of being really busy with work and messed up our plans. He was upset at himself and felt like he wasnt giving me waht I needed. He wanted to stay in contact which now seems obvious that he did it to keep me around for when he could commit. I recieved random messages, then cut it off. But then we saw eachother again. Finaly the messages were less and less. Util one very radndom month I recieved a message from him to go somehwere where he was, etc. I said I was busy. I never gave me my time. Years later, 3 to be spesific, I see him downtown while I was with my friends and he was with his new girlfriend. He looked at me, I turned away. We at one point were walking in the same direction, into the same location and he was standing right next to me. I could feel him wanting to ackowledge him, but I didn't. I was over him and happy. I think a month or so later, his friend pocket dialed me and we spoke a bit. Due to that I thought about him and sent the guy I had dated a private facebook message (no call, no text, not even a friend add) "your friend pocket dialed me last week and you came to mind. I don't want you to think Im starting anything because you know I'm not like that. Honestly you don't even have to respond if you feel uncomfortable. I remmber you getting stressed all the time for work and honestly life is to short. I hope life is well and i know when it comes to finding love you'll have no trouble i that department.
keep it fresh my friend.
ps i saw a band we mutually like in concert, i cried..."

This is essentially, ball-park what I wrote.
He never responded. At the time I didnt care at all, i felt like maybe I was reaching out in a "im releasing you" sort of way. I was happy. 10 months later, I am mortiifed that I ever sent him a message. I don't know why? He is still with that girlfriend and I'm sure they're happy. I am so angry with myself, jelous (ill admit it) that they worked out and we didn't. I feel like Im the pathetic girl from his past contacting him. Just as other girls he mentioned did a few times while we were dating (he had a psycho ex). I was dating this prick that had known him, but aren't friends. And i think I kept dating him because I liked that they knew eachtoehr. I wanted him to oneday run into us together and see I've moved on. But I have no one and havne't really since him. I didn't even have him, I've had no one always. And feel absolutely pathetic that I messaged him! Am i pathetic? Is this normal behavoir? I'm mortiifed, 10 months later...go figure. Also, it makes sense that he wouldn't message me because he is with someone he obviously does not care about me.