It has been a year of training for me running at 20 MPW. When I started running, I could run a mile in around 9 minutes. Now, I just ran a mile in 8:05 minutes. I was dying at the end of the mile. I am 18, male, 150 Ib, and 6'0''. I don't get why I am so slow. Most HS track kids could run a sub 6 minute mile with that training. Why am I so slow? What is wrong with my training?