Liking someone else?

Hi,

I've been with my boyfriend for 6 years. He is my first boyfriend.
This story goes back to before we were even together. To summarise it, I liked him when we first met in college and we started talking due to the fact that we had some courses where we shared the same class. One day, I saw him at the canteen with a guy, his friend. And that point in my life, it changed because I realised that I liked his friend. (I didn't realise this until a long time later). I found myself always noticing his friend subconsciously and wanting to get to know him.

Eventually, I ended up with my boyfriend of course and he introduced me to his friends, which included that guy. Let's call him M. I became friends with M and soon after we exchanged contacts and have chats from time to time. I always felt this adrenaline rush everytime I talked to him. Even when he got a girlfriend or when he kept changing partners, I still felt the same way. There were certain points in time where I felt that he was attracted to me too in the past.

However, one incident happened which made us (me and M) get into an argument and things got awkward from there on. We've since graduated from that school and no longer meet each other but we still do see each other probably 1-2 a year when there's a gathering. I have never been able to forget about him. It's been 6 years now. Sometimes I question myself if I made the wrong choice of getting together with my boyfriend instead of M..

Point is, I have tried ways to get over M. I still can't. Despite not staying in contact with him and not seeing him for a long time, my thoughts still ponder about him. It is really queer. I understand I'm not being fair to my boyfriend about this. Which is why I'd like to get some answers from someone from a neutral point of view. Any feedback or advice would be great. Thank you.