Have you tried running outdoors? I've gone from running only 1 minute at a time to running 1mile in under 9 minutes, im sure the time will be a lot less on the threadmill as I havent got uphill, wind, stoplights amongst other things to slow me down, plus im over 200lbs. So im sure if you incorporate outdoors into your training, im sure you'll become a better athlete becomes a reduce your time.