My cat - out of the blue - started peeing on all the dog beds and anything left on the floor. She has NEVER done anything like that before. I noticed she was straining to go and was only going small amounts.
I finally took her to the vet yesterday and $122.00 later found out she had an UTI. The vet said she had a bunch of blood and bacteria in her bladder. Now she is on antibiotics. I noticed a tiny pee on the floor today that had blood in it. I hope the meds start helping fast.
So, it could be someting like that or one of the other things suggested. It's good you got her checked out, though.