I think that it must be hard to start at the very beginning again. With the first tkr, you didn't know what was coming, everything was new and you didn't expect as much from yourself. This time (probably subconsciously) you expect yourself to know what to do and expect it to happen quicker. I know that I was blindsided by the pain the first week until I got the med schedule down. You WILL get a handle on this and you WILL get better. And you WILL NEVER have to do this again.
I'll be praying for an easier day for you today. Take those meds, rest, ice, elevate, and give yourself a break. Hugs.