You're not running 100mpw, you're not running twice a day, stop being a p**sy and run faster.
I went from a 17:05 5k to 16:11 5k in 3 months after I stopped doing easy runs at 8 min mile pace and started doing them at 7min pace or even sub 7 on some runs, this was on top of 3 hard workouts a week.
Slow running makes slow runners.