I Have Been Having Pain In My Legs - It

I have been having pain in my legs - it started in my left shin area, but now has moved up to include the whole leg. It is worse at night, and sometimes wakes me up. It is also worse when sitting. I am a breast cancer survivor and had an xray about 6 months ago to rule out mets, but it didn't show anything abnormal. The pain comes and goes, but can be quite painful at times.