I have been taking phentermine HCl 37.5 for weightloss about 3 days now. I have lost no weight and im wondering if I ever will on this. Help please?

Not by itself. Phentermine at best will help suppress appetite. In addition to the medication you need to work on limiting food intake and getting regular exercise to burn calories. Please calculate your body mass index and if it reaches 22 or less, stop the phentermine. I worry about eating disorders in girls your age. Take Phentermine only if your doctor recommends it (please!).
Stop Phentermine. Please stop this dangerous drug. It will not lead to any real or lasting weight loss. It is dangerous to your health. Anyone who prescribed this for you should be fired immediately and you should find a caring and frank physician who will treat you with respect and honesty.