What does it mean to have pains down outside of legs, tender elbows, & low blood platelettes?

Many possibilities: One possibility would be some sort of autoimmune disease that causes sore joints, since many of these can also cause low platelet counts. Low platelets can be caused by a destructive process or by a production problem. Tying this in with the other symptoms you describe will require a careful medical history and examination. I hope you better soon.