Hi welcome to health care magic forum, The knee joint swelling with out pain is not a thing to be worried. High C Reactive proteine and ESR
may not have a role in your case. C Reactive proteine in children will cause knee swelling with pain, presence of it at this age signifies that it might be there sinse child hood, and caused heart deformity
. As you states it is un diagnised problem it could be a psychological problem also.
Your gastric problem besides medication needs some diet recommendations as Take more of green leafy vegetables, avoid taking more of chillies, spices, junk foods, and figh fat foods.
What is left is head ache and pains of sourounding parts. It could be sinutis, or refractive error
Wishing for a quick recovery and thanks for calling.