I agree with Ramses. I switched from Prempro to Estradiol, which is a natural hormone, and felt so much better. Another possibility may be that you are underestimating how much you eat. If you don't feed your body enough, your blood sugars do drop in many cases, and this could cause the tired, sluggish feeling. Plus, if you are not getting enough protein, your body will either hold on to the fat, or burn muscle instead of fat.