No Energy, Pre Op Diet

I have absolutely no energy on this pre op diet. I can only have Protein Shakes, Water, Zero Calorie/Zero Sugar drinks/enhancers, Sugar Free Popsicles and Jello, and Low Sodium broths. I am meeting my daily protein goal, my daily water intake, and taking all my vitamins. Somebody mentioned iron and I called my surgeon's office and they said there is no need to take iron right now and that they will check those levels 3 months out. I'm just worried because my iron runs low and I am exhausted, dizzy, and weak all the time. I have 5 more days to go on this clear liquid diet. My hunger really isn't even an issue, the water and protein keep me at bay (most) of the time. Does anybody have any other suggestions? Thank you!