Feeling As Though I Am Having Low Blood Sugar, But

Feeling as though I am having low blood sugar, but my blood sugar is within normal range. Just had pneumonia and am never sick. I feel like I am starving even though I have just eaten. Legs are weak and am very shaky. Have no energy, can hardly put one foot in front of the other. I usually walk every day and am usually very energetic. I must add I am 76 yrs. old.