I agree. 7:00 is not crazy fast at 53. I'm 64 and just did a solo 10k time trial at 6:38, and I've done a 10 miler training run this year at 7:15 and I'm a long way from being exceptional.
Absolutely no doubt that the first thing to do is to get a complete medical work up. The shallow fast breathing would be a major red-flag.
If the medical is all clear, then it's possible you could get that way with too much anaerobic training,