Realationship issues?

Okay, I'm 20 and I'm curious what the masses think about how I acted in my most recent, and longest relationship ( 2 years)

First off it was fine, but about a year in we started arguing about the way she was acting. There was this guy, who I knew beyond a doubt that wanted my g/f. He flat out told a very good friend of mine. Everyday between classes I would see him leaning over her at her locker, definitely within the "presonal bubble". They would hangout all the time and all that. She just dismissed that anything was going on, and say I was being stupid when I wanted her to stop hanging out with him.

Eventually I gave her an ultimatum, him or me, this is past my comfort zone, so that's the choice. She did stop hanging out with him.

But, she started a new job, and started hanging out with this guy that I didn't know at all. Would go spend the entire day "shopping" in London, Ontario. Me and her had eachothers email passwords, and facebook, one day I went on her email because I had some pictures stored of my truck and I needed them. I noticed that there was over 80 deleted emails (hotmail, it shows up in the corner), curious I looked and about 3/4 were from this guy, over the course of a couple months.

They would talk about every little dirty detail of our relationship, she'd tell a story about a fight, where as far as I'm concerned, she was totally in the wrong. But she would skip over that part. I have a pet peeve about people saying they will do things, and then never doing them, we fought about that the most.

At the end of most of the emails it would be signed "Luff You", which was way way too much for me.

I confronted her, and we talked, a lot. She made all kinds of promises, respect my wishes and all that. But within a few months she dumped me for a friend of mine ( no longer a friend), saying I was too controlling?

So, that is as close to the truth as I remember it, because it's not like I know any of your people. Was I too controlling? Or mostly in the right?

I'm asking for future reference with my next g/f.