Why Do I Have Severe Muscular Pain In The Upper Right Hand Side While Recovering From Flu Symptoms?

I have severe muscular pain upper right hand side. I have had MRI, chest xrays and blood tests and they have come back all clear. Now I am enduring muscle spasms with pain. I have had the flu four weekz ago and these muscle spasms had started within a week of getting over the flu. Can I get some advice