Without sharing TMI, let me just say the first week was very interesting bathroom-wise.
I forced myself to eat - just plain turkey sandwiches but it was at least something. Legs were shaky, lots of anxiety. I spent the better part of the first week holed up in my bedroom watching TV.
As others have said we abused our bodies for so long that it's going to take time. Glad to hear your doctor is aware.
It DOES get better! Congrats on taking that first step!!