I was very discouraged about 3 months in and I talked to my doctor about it.
Everyone I talked to that had a replacement was telling me how great it was and how they were pretty much back to normal in 6 weeks, or 10 weeks or 12 weeks.... my MD said, no they weren't. It takes 6 months to a year for recovery and that means getting over pain and discomfort and regaining flexibility. My MD did not understand why, but virtually everyone who gets a knee replacement seems to forget how long it took to recover. Later my physical therapist told me pretty much the same thing when I was getting depressed about it.
However one very important thing is physical therapy and doing all your exercises religiously and often. Especially the flexibility ones. It hurts, but you have to do it. And long bouts of sitting normally can be a bad thing
Something I noticed. I have been dealing with knee and joint issues for over 12 years and the body will, without you noticing, change the way you move to avoid pain. Other times you consciously change things or stop moving a certain way to avoid pain. That is a hard thing, at least for me, to retrain. I have had to do gait training to retrain myself to walk properly and I have had to not avoid pain in the replaced knee, that prior to the replacement I had to avoid because it was a bad thing. The pain in the replaced knee can be a good thing, at times, can mean you are breaking up scar tissue or it could be pointing out where you need to work on breaking up scar tissue. However there are pains that you need to tell your MD about immediately too.
However at just over 6 months, the lack of a good night sleep is still an issue and the pain, for what appears to be no reason, at 3:00am is not fun and I still can't convince myself its a good thing
I hope 2022 is better.