You are only 17. Boys this age have the attention span of a gnat (girls often, too). That you have been together over a year is unusual, given your developmental levels. I wouldn't expect any relationship with kids your age to last more than that.... you are both growing and developing into (eventual) adults, and your paths have not lead in the same direction. Your needs change. This doesn't make either of you the bad guy; it's just the way things go at your age.
Relax... I'll need some information first. Just the basic facts - can you show me where it hurts?