It has ruined my relationship....How do I fix this?

KML
you are not broken. you are however young and experienced. I'm thinking young people make mistakes in relationships (hell older people do as well) and learn from them regardless of whether they have AD issues or not. it is part of growing up and some things take time and maturity.
it doesn't seem to me this guy was as serious about the relationship or as mature as you may have originally thought. if he was he likely would have worked thing out.
also keep in mind many guys lie. they tell girls what they think we want to hear and dont show there true intent until later on. this is likely the reason so many girls have trust issues and baggage to bring to the next relationship. (it all guys fault lol) girls will do it to though.
also consider the fact that you may not have been upset over trivial things. what ever was going on was really important and hurtful to you at the time. i can see where you are looking back on things saying that was really stupid to be mad about but you arnt really sure. it is possible you are making excuses for him so you can blame yourself for his behavior. your dad left when you where young and its possible you took responsibility for it because lets face it almost everyone hear my self included tryes to take responsibility for the actions of others.. if not currently we likely did at your age. it hurt less for some reason if you can make it all your fault then you dont have to feel hurt because someone else made you feel hurt.
just some thoughts.