PCs to 29 palms can’t run for shit

I pcs from Washington state to 29 palms and it’s Been about two weeks I’m running 8 miles a week on pcs leave lifting everyday and we did our first pt and I could barely keep up is it because I’m out of shape or is the climate change significant in Washington state I was running 21 minute 3 mile and I’m not overweight any advice I am also eating clean and hydrating