If the miles were passed at 6:0x, 12:5x, 20:5x, like the other poster said that is 6, 7, 8. Even if the 20:5x is 5k you were 6:0x, 6:5x, 7:20. It should be easy to understand that 7:20, 6:5x, 6:0x is easier than 6:0x, 6:5x, 7:20.
So try to run the first mile of the next race in 7:20, it shouldn't feel like you are pushing AT ALL. The excitement of the race and fear that you are going out too slow will get you to 1 mile in 7:20 pain free.
In the second mile try to pick up the pace just enough to run 6:5x. You will know you are starting to work but compared to 6:0x, 6:5x, 7:20 you will feel under control. With 1 or 1.1 to go, pretend you are racing the mile. Pick your knees up and go. You need to hurt the entire last mile.
This plan WILL fail miserably. I can't tell you why. There will be a big hill in the wrong place. Your first 7:20 will end up 6:4x. It will be hot and even 7:20 will feel bad. The point is that your splits will NOT be what you are trying to run.
Even though the plan fails, you will be flying the last mile compared to your 7:20 or 8. That will be FUN and will let you beat some guys you didn't last time. From where you are that is the best you can hope for. Good luck