I Have Been Experiencing Severe Pain In My Legs (especially

I have been experiencing severe pain in my legs (especially left) when I stand for more than 5 minutes. It subsides when I sit down. I have been to a chiropractor who no results. I saw our small town nurse practitioner who ruled out blood clot or verical veins ... Thought it was just muscle strain. However it is going on for over a week ... Seems to be getting worse. Any suggestions? I've been living on Aleve for pain. Thanks