My first tours were miserable. I didn't even carry water on the first one 40 years ago, I was that green. And attempting to sleep at a campground in Maine in 80 degree heat and 80% humidity and clouds of mosquitoes and no tent resulted in standing in the shower, water running to keep the mosquitoes away, most of the night. Sort of surprising I ever wanted to ride a bike again.
As for the knee issues you might want to check your
saddle height.