I am now just over 7 months TKR.
It is definitely a painful recovery (for a couple weeks). My incision was quite painful for some time. It was my left knee. Using a body pillow between my legs and sleeping on my right side helped while trying to sleep. It does get better.
Most importantly, for complete healing keep up with those exercises and physio therapy even if you have to push through the pain. Don’t forget ice. You are not alone. Two weeks post surgery, I was taking a short walk (on crutches) and met up with a gentleman half my age that had a TKR a couple years prior. He shared that he was in such pain post surgery that he was leaning against a wall literally in tears from the pain.
The incision pain will improve. Getting the staples removed after 2 weeks also helped with the incision pain. Within the first few weeks I did wonder if it was worth getting the surgery.
It didn’t take long before I became grateful for getting it replaced. Now 7 months in I can honestly state that it’s the best thing I ever did. Full ROM and no pain. Minor stiffness only.

The first month or so after tkr is very painful. Don’t be afraid to ask for a refills on the meds. It’s important to do your pt and walk around. I know with my 1st tkr I was in a lot of pain. It was kinda shocking to me how painful it was. Knee replacement is a big surgery and it just takes time (a year they say) to totally recover. I had my other knee done in late August last year and it’s fine now unless I go up and down the stairs a lot. I get some throbbing pain at night if I overdo it. Just rest, use a lot of ice, elevate and enjoy not having to do too much. Watch tv, read, distract yourself if you can. It’ll get better. I know it really is painful but one day you’ll be glad you did it. Hang in!