Help for an older runner with significant leg pain?

Hey runnit, I'm a 47 year old male life-long runner who has started to develop some significant leg pain over the last couple of years. I currently run 4 miles x5 days per week. For about the last 3 to 6 months I have had increasing pain in my calves (7 to 8 intensity on a scale of 10), and to a lesser extent my lower back (5/10 intensity), knees (3/10), and ankles (1-2/10). I used to do mainly trail running, but the twists and turns and ups and downs seem to make the pain worse. The pain is really slowing me down and making my daily run a lot less fun. I tried cutting down to 3 miles but it didn't seem to help. The pain generally improves somewhat afte 2 miles.

Any older runners out there who have experienced this, and who have any good tips?