wrong technique?

1. Maybe you need the to fix some of your swimming technique.
2. After finish a lap, reduce the resting time and keep pushing yourself to do the next lap.

Freestyle breathing technique the best is to breath every 2 strokes. The purpose is to prevent your body getting out of air and sink. When you're getting out of air you'll be out of energy thus hard to swim longer distance. For sprinting it's different, because it's short distance, you can choose to breath every 2 to 4 strokes. The purpose is to reduce head movement thus reduce drag. Anyway you can watch how the Olympic swimmers swim freestyle on youtube to get some idea. Learn from the best. Cheers.