Diamond54

How much are you drinking? Dehydration is easy in the beginning. Make sure you're drinking everything you're supposed to. Some tiredness and weakness is to be expected. You're not consuming very many calories. As long as you're staying properly hydrated, this will pass.
I'm still pre-surg, but I will be on full liquids for 2 weeks after my surgery. So, I'll be where you are, in 8 days.