Problem with 20m Bleep Test.?

Hi, I'm getting sleepless nights as in 3 weeks time I have to achieve 8.6 in Shuttle Run. I do a lot of Kickboxing, but just can't run! I've got the Bleep Test and train 2x a day in my alleyway and just can't get p 6.2! Please help me, as if I fal my dream of being a Firefighter will vanish. Thank you.