Time yourself...sometimes you feel like you are slowing down, but you really aren't.
Sounds like you need to run more suicides and build up your stamina
In HS, the 2 minute drill was always a killer. Any drill with a vomit can stationed at mid-court can't be too much fun. We went end to end on a basketball court and had to do 10 down and backs in under 2 minutes. We had to do one extra of them each time someone didn't finish in under 2 minutes or until someone puked. If you didn't finish in under 2 minutes the first two times, you weren't going to do it the 3rd time. That's where the trash can came in