Thanks for your question.
Are you consulting a therapist? What difficulty are you facing in gaining weight?
Thanks for your reply.
Basically the weight that you can maintain without dieting and restrained eating and also without exercising for the sake of weight control, then that weight is your ideal weight. Your ideal body weight preferably should be 8 stones or more. Always good to have a higher goal in eating disorders than the general population.
Therapy is a must to know how to deal with your thoughts about your body in a better way. So continue the counseling. Also you may read the below linked book:
Please rate the answer with a positive rating by clicking 5 stars.
What I meant is that your BMI (Body mass index) should be more than the lower normal range of BMI. Normal BMI In adults is 18.5 to 24.9 and you should aim for a BMI of 20.
You need to consult your doctor before starting any exercise program for osteoporosis. It is normally recommended to exercise when is having osteoporosis, but one needs to avoid high impact exercises. Running should be OK.