I am a healthy, fit 55 year old, so the pain is new for me. The pain seems to be worst in my lower thigh. Any ideas?
This could be something called sciatica or something close to it. In sciatica the nerves the run down the back of the legs to the foot get compressed where they leave the lower back.
This compression can cause pain, tingling or numbness all the way down to the foot, although I would think that's pretty rare. Usually the pain is in the lower back, buttocks and upper thighs and it usually occurs on one side, but can occur in both, although that's pretty rare
Here are the symptoms of sciatica
It sounds like it's time to see a doctor and see what's up. Good luck!
Here are some links on pain management that you might find useful as you're dealing with this:
Using Tylenol Responsibly
Let’s Talk Pain Meds
7 Surprising Causes of Back Pain