Discomfort In The Lower Back On Both Sides. Difficulty Walking

Discomfort in the lower back on both sides. Difficulty walking comes and goes. Very difficult to stay hydrated and become tired by mid morning. Urine continues to be yellow... urinate every hour or so even during daytime. Lower back and legs seem stiff and legs feel weak. Symptoms are reduced when I can stay hydrated but that seems difficult to do. Had recent PSA test ... (.04) not even up to 1.0 Platelet count low at 120.