Cat issue

Ok so my cat has been urinating on the carpet. I don't know why she does this. I keep her litter box clean which she will defecate in but not urinate. It is always by or near the same spot. By the back door. I can't seem to get the stains and odor out of the carpet. Anyone have any ideas? I have tried resolve powder, nature's miracle, and many others. My entire living room smells like cat urine. I need to find a way to get rid of it. The thing is, it is very hard to get rid of the smell. If anyone has any ideas then please let me know for I will try anything.