Hello im a 17 year old girl, who is 5ft 7 and im weighing 105 pound and still losing weight, is there anything I could do to stop this?

Need evaluation. I can exclude the main psychological condition causing weight loss, anorexia nervosa, as these people tell themselves that the more skeletal they appear, the better they look, and hove no concerns. You are concerned, and you need a complete evaluation by your PCP to see if something serious is occurring--much too complex for an evaluation here. Hyperthyroidism is one of dozens of possibilities.