Hi. I am a five foot zero teen weighing nine stone. Have pain down in lower back, on the right hand side, going down the top of the butt and through the outer thigh. Gets worse when walking or sitting for an extended period. Also have pain on the outer sides of my knee, particularly when going down stairs. Knees feel sometimes as though they are going to buckle, and have noticed burning sensation after prolonged periods of standing. Also, get general random pains, as well as a sensation of pressure being applied under the left side of the ribcage. Is this all caused by being overweight? Or do i have a problem with my muscles?