I am feeling really confused at the moment and just wanted to vent here to see if anybody else has felt like this and if so, what the outcome was.
For background context, I've been with my partner for 10 years and we have 2 young children. I love him so much, but I can't stop thinking about somebody else from my past.
I met the other person when I was a teenager. We clicked instantly, it felt like we just "got" each other and we spent a lot of time together when we were younger (we had the same friendship group). We knew so much about each other but we never had a relationship. Back then, I wasn't sure if I was sexually attracted to him. But even without that, I felt a strong connection with him. I knew he wanted more at the time and I think he tried to just accept that we would be friends instead. Then I met my current partner, and gradually I stopped being close with the other person. It was getting complicated and the lines were becoming blurred. We spoke over the years briefly and the connection was still there, but nothing romantic happened. It was just as friends but it was honestly difficult to keep it that way. I know this sounds bad but I never cheated.
Over the years I have thought about him but put it all at the back of my mind, he was a massive part of my life up but more recently I just can't seem to stop thinking about him. He is with somebody else now too. The worst thing is, he lives locally to me and I see him often. He is in my dreams a lot and I wake up feeling worse.
I don't know why I feel like this. I love my partner, he's the father of my kids and we have been together for a long time but he's never understood me the way the other person did.
I feel so confused and I don't know how I can stop thinking about him. Or why I even still am after all these years 
Anybody else been in similar situation?