I Am Having Severe Muscle Pain From The Hip To

I am having severe muscle pain from the hip to mid-thigh. More severe on the right side but also comes ad goes on the left side. Pain will sometimes extend downward to calf. Pain worsens the longer I am on my feet. I prolonged rest either overnight or in a recliner helps the pain reduce but it reappears once I am up and about again. Is there a likely cause?