Gidday Chas, I kind of agree with Shamou. You say:
'The years came flooding back'
and later in your post:
'I also ask myself why I am always the loser. If I was looking at him, well then I ask myself, did he have the right to deal with the threat he was facing, in which case he was not the bully. I have so many unanswered questions and being a little compulsive over something like this, it goes through my mind incessently, with my head turning like a tumble dryer on high spin.
I suppose if I felt that I had won this battle, it would have all sunk away as fast as it happened.'
What happened to you as a kid was obviously serious enough to have had a lasting impression. As kids, (especially without good help or guidance) we can form solutions and adopt beliefs, consciously and unconsciously, regarding serious incidents that work ingeniously well to keep us safe at the time. However, the ingenious solutions that little kids come up with to keep safe, and that were applicable at the time, don't always work well or apply for adults, in adult situations.
If you believe in 'the law of attraction', or that your thoughts create, or that your thoughts shape, or influence your life, then holding deep beliefs about yourself as 'always the loser' etc aren't much use, unless you enjoy experiencing and creating a life along those lines.
The deluxe side is, that you have had a situation arise that highlights something that you would like to, and can change. Rather than your thoughts, 'going through my mind incessently, with my head turning like a tumble dryer on high spin', and controlling you, you can take responsibility for them, and choose to control them and work on thinking things that are more valuable to you. For instance, you could notice the thoughts arising, accept and realise that you are generating them, and that it takes power to do so, (you), and decide to use your power to generate new, pleasureable thoughts. Maybe you could think how well you did to actually deal with the situation and walk away with both yourself and the other guy unscathed. Or you could remind yourself that a situation like that once in twenty years reflects pretty well on you.
I tend to think that self esteem work is at the crux of a lot of things. For me, to label yourself in writing the way you have, says that your self esteem could be better, and might have taken a dent as a kid being bullied. Maybe the dent was never repaired, or maybe something else added to it, or something entirely unrelated may have caused you to think of yourself as losing. Improving your self esteem would have a flow on effect in every area of your life. There's literally tons of ways, and tons of great books and teachers that are available to improve your self esteem. One of them will appeal to you. One technique that I like is that approach in a thread 'The Magic Pill' on this site. It is so simple and direct, and seemingly effortless, like a lot of profound or ingenious things. You'll find something if you want, where's there's a will there's a way!
So, like Shamou, I agree, it's up to you to choose how to react to the bully. Bullying isn't good, and I am genuinely sorry that you were in that situation, but choosing to be affected in a good way that empowers you can have amasing results. I believe that you'll have the full weight of 'The Universe', Spirit, God, Yourself, whatever you call it, behind you. All the best!