I've been having pain since my tkr 5 yrs ago and the right side of my knee is still tender, what's wrong?

Many reasons... 90-95% of knee replacements are still functioning after 15 years. Some of these are still painful, however. Pain can be from infection, loosening, malalignment, mechanical wear, instability, allergic reaction, or nerve or muscle problems not related to the actual implant, among many other possibilities. You should discuss this with your physician, and seek a second opinion if necessary.
Depends. Hard to say without seeing xrays and examining your knee. It is important to remember that this is a man-made device, and it will never be as good as your knee was when you were in your teens or 20s. If it isn't better, or worse than pre-op, then you should be re-evaluated by your surgeon.