Help! Toxic love!

I am married to an amazing man that loves me, is my best friend, supports me whatever I do, and would die for me. I feel very lucky to have such an amazing influence in my life and know that he is absolutely irreplaceable. However, four years ago, I was walking to work and became aware of a man staring at me. I looked over and it instantly felt like I have been hit with a tonne weight. I felt immense passion and attraction that I had never felt before in my life and I could see that he felt the same. I walked by thinking that I probably wouldn