I'll tell you a little story
Before I started dieting, I was about 17 - 5ft 8 and 12 st 7b. Slightly overweight.
I restricted my food heavily and went to 8st in the space of a year... NOT sustainable. I lost muscle mass and flushed my metabolism down the drain.
Now I am 10st7 and look the same as when I was about 12 stone, because I lost all my muscle mass and gained pretty much pure blubber.
Long story short stop focusing on the scale and focus on cleaning up your diet and exercising - at any weight, and at any age. For your health. This should be the leanest part of your life, so learn healthy habits now and you won't be 14 stone in 4 years time.