This is a very rough situation.
No, there is no way we can diagnose you, but I can comment on this.
I believe the bone scan should be done.
This can pick up infection that the MRI can miss.
I would not wait longer than 2 or 3 months to do it.
I would prefer this over an MRI with contrast at this point.
Other causes of fever can be an abdominal abscess: CT scan needed.
Or, endocarditis, an infection of the heart valve, echocardiogram needed.
It can also be a problem with temperature control, such as from a brain tumor, but this would generally give other symptoms.
I would sit down with your main doctor and go over these possibilities.
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