Mike, first of all you need to understand the difference between someone giving you good realistic advice, and someone being sarcastic and on a wind up.
The guy who said keep up with 1st place also said you'd be a top triathlete, and would crack 2hr 20 for a marathon! Check out the power of 10 website and see how many UK men do that each year!
You found out today what we've all found out. Run well above your limit and you simply blow up!! That's what's given the breathing and chest issues.
Next race, understand that 18.48 is your pb, and have a vague idea that the km pace is 3.45 per split.
Then, if you find yourself going through kms in 3.30s you're likely to be on course to blow up again.
Pacing is the most key thing you'll ever learn in racing.
Gentle up in mileage certainly won't hurt. You could do worse than doing some KM reps in training too at 3.45 pace (your current 5k pace)
Edited: 04/08/2012 at 17:00