Hey sorry to hear about your problem. We all here have the same problem, some worse than others and we do know how you feel. I have it aswell, expect i can't smell myself and my doctor believes mine is coming from my sinuses so i'll be doing a turbinectomy and really don't know if its going to work. I'm also 15 and have had it for about 2 years now and life sucks with it - I lost most of my friends, got no social life and my grades are starting to fail.
Since you mentioned that yours seems to be less intensful when you eat nothing then it could possibly be from the fecal matter in your colon. I'm not sure how to permanently fix this could be damaged sphinter etc I'm not sure but if your interested in finding a way to eliminate waste odor you can try chlorophyll supplements. It's a body deodorizer / alkalizer and will get rid of the smell of your waste including your perspiration etc. However, for the first couple of days (maybe 3-4 max) you will smell worse because it's expelling all the waste in your body that has built up. Read more about chlorophyll here http://www.energiseforlife.com/wordpress/2009/02/11/health-benefits-of-liquid...
and as always please please do talk your doctor before doing anything and if your going to buy chlorophyll always buy it in liquid form (much stronger). As for dosage, I'd reccomend starting at 75mg a day for a week, then go to 150mg the next week and stay at 300mg after that. I'm positive this would help, do try it and keep us updated.
Another thing you might be interested to try if the above doesn't work is digestive enzyme supplements.