Should I apologize to him?

Sorry about the length! I really need some advice.

There was a guy (I'll call him Fred) I liked since I met him in 4th grade. I thought he wasn't interested in me all those years, so in my junior year of high school, I started dating someone (Bob).

Although I honestly did like Bob, Fred was always in my mind. I always wanted to be with Fred more than anyone else; Bob was kind of just filling a void.

So Fred and I had a couple classes together that year, and we became good friends. It became fairly clear that Fred had strong feelings for me. I wasn't entirely sure, but I knew that I wasn't happy with Bob and that I should take a chance with Fred.

I broke up with Bob about 5 months after we started dating, and then starting dating Fred a month later. Bob was really crushed (I told him the truth why I was breaking up with him), and I felt awful even though I was much happier without him.

I was physically faithful to Bob, but in an emotional sense, I was quite unfaithful. I was in love with Fred, but stayed with Bob until I was more certain things with Fred would work out. I guess my mentality was that if Fred didn't like me, I'd always have Bob to fall back on. It is wrong, I'll admit.

Which brings me to my question. Even though it's been 9+ months since I talked to Bob, I still feel somewhat guilty for being emotionally insincere and unfaithful.

Should I apologize to Bob? I'm not trying to salvage a relationship or even be friends, I just feel like I should atone for what I did to him. I was never fully committed to that relationship, and it's wrong to do that to another person.

It's an abstract thing to apologize for. I don't know if it would do any good. I guess it would make me feel better inside, but I don't want to hurt Bob's feelings even more by telling him that I never really wanted to be with him in the first place.

Should I say I'm sorry, or should I focus on trying to forgive myself instead?