At 5'9" and 115 lbs, your BMI (body mass index) is less than 17. You are significantly underweight. BMI is not a perfect measure, but there is no world in which you are not seriously underweight already. 105lbs is not a reasonable goal.

I think you should consider that you may have an eating disorder, or you may be getting a little OCD about body management. Please talk to your Pdoc ASAP.