How to identify IPF?

Hello doctor,

I was diagnosed with IPF last week. My two x-rays, two lung function tests and HRCT scan showing that I had scarring. But I am confused, because I feel better than I have felt in 10 years. I have always smoked and had cough for years. I have been on a diet and have lost one stone so far. I have been doing some tests at home such as at rest I can hold breath for 1 minute 25 seconds with relative ease. Breaths per minute sitting at rest are 15 and my blood oxygen levels at rest are between 95 to 99 percent. Running up and down stairs three times my blood oxygen levels drop to around 91 to 92 percent and it rises to 95 to 96 percent in less than a minute. When I wake up in the morning my blood oxygen levels have been around 86 percent rising to 92 to 94 percent in around two to three minutes. The other thing is that when I had my second lung function test five months ago I was at the end of a cold or flu. I did mention this to the consultant. Do you think I could have been misdiagnosed? Is it worth me asking for a second opinion? Please guide.