Am i over - excersising??

i run 7 - 12 miles a day ,even when i get tired i keep running because the demand to lose weight keeps me going. i do about 4 hours of excersise every day. i run in any condition including the extreme summer heat here in death valley. i am 14 years old and im 220 lbs 5 feet 8 inches tall. My first wake up call was about last week when i was playing xbox and i could hear my heavy breathing in the silence. also i can't tie my shoes without a chair anymore so i started running , the first 2 days were looking bad i was having aches and soreness but i kept going even when i lost my breath and was sore, now it dosent bother me at all. i actually feel more mobile now and i feel fantastic after 7 miles ,i feel like i could keep going but the heat gets scary out here. i also do 10 push ups and 50 sit ups. I am not starving myself but i only eat when im hungry , i used to eat things just because they looked yummy and not because i was hungry. but i have changed ..will i effectivly lose weight by december? if so whats your estimate of what my weight wil be in december. i have lost 3 lbs already in just 7 days.