Explain how my PFTs went from 111% last month to 94% today

I'm sad and confused. How does this happen?? Last time I got my PFT was from my general doctor using some fancy handheld one I got 111% , and now at my CF clinic with their bulky computer and special nose plug and what not I scored 94%. It's depressing and confusing. explaon this to me please! the only thing that has changed since the PFT done a month (and a half) ago and now is I go to the gym 4 days a week whereas before I'd go 3 days a week. For for the past few days, it's been remarkably windy btw. Everyone here has been talking about how it's so windy and we even had a little dust storm (that was video taped and put on the news). Just something to consider. Oh and my back hurts and my abs are sore from working out.
Source: Cystic Fibrosis Exercise and Fitness Forum - Category: Respiratory Medicine Authors: Tags: Exercise & Fitness Source Type: forums