I just turned 15 and ran track during my freshman year. I got run into the ground because of the workouts (all sprints), but still managed to run a decent time. I took a month off and then resumed with base building, mixing distance runs of 10 miles + with shorter distance tempos (built up from 20 to 50 MPW quickly). During a 1 hour tempo-type run, I started to feel like crap and on all my runs I feel unenergetic and weak, and have problems breathing. This is exactly how I felt after my track season. Is this burnout or fatigue? I want to get better this year, but I can barely finish my practices now.