I think when you go to your race and look around, you will be surprised at how many "over weight" runners there are.
It's funny, but my perception of whether I was "fatter", or "thinner" than my fellow runners during any one race was a real reflection of how I was feeling about myself at that time. I am sure that the population of runners really wasn't changing much (nor was my weight), but there were times when I was sure that I was the fattest thing in Nikes, and times when I (privately) scoffed at pudgy plodders lining up at the starting lines.
I have learned so much about myself from this sport! I bet you will too. Keep up the training. I admire your perserverence in the freezing midwest winters!