17lbs in 30 days!

Age: 18
Height: 174cm : 5 '9 ft.
Exercise: 30 mins per night cardio for 5 nights then 2 off . 15 mins abs per night for 5 nights then 2 off

Reason: have to be 17lbs lighter due to work. I need some pointers. I am able to get to 137lbs but cannot get any lower...currently a size 9-10 in pants UK size. Need to be 6-8 ABSOLUTE max!!
Dietting tips?

I do 20 mins of yoga in the morning and refuse to get a personal trainer because i dont believe you should pay for motivation..
Just need a few tips on losing weight and keeping it off and good subs to stop any cravings.
17lbs in 4 weeks!!
Please leave some feed back.
Thanks.