My dog has always been fearful, now that she's older i can't even get her to go out to pee.....?

alot of times she'll just pee on her bed....i have to go out with her. i got her from a puppy and she spent 10 weeks with her mother so no reasons there. my vet has told me it could just be her breed...she's a mutt, so no reason there. she gets worse as she gets older. she's 13 and is now suffering from early stages of kidney failure....i love her, i just wish i knew why she has always been like this.