When we broke it off i lost everything because when we were together i lost my priorities.
It took me a while to understand this... I see what you mean. He had taken up 90% of your attention and provided 90% of your fulfillment.
Well, the reason you think it is a stupid topic is probably that you intuit the fact that adults have trouble taking teenage relationships seriously. We say, "Oh, there are other fish in the sea" and stupid stuff like that. But actually, you can make this a great topic. Here is how:
Do not make it about YOUR relationship, but instead make it about your experience of discovering this phenomenon, this tendency of people to invest all their eggs in the basket of a boyfriend/girlfriend, and then lose their identity in the process.
This is a common human problem, and you now have great insight into it. Write this not about you and your relationship with all its details, etc. but instead about human nature and a tough lesson to learn.
And mention your professional goals! Remember, you will be a professional in your chosen field just a few summers and winters from now... like 5 or something. So get ready! Make this all about getting back on track academically and professionally. :-)