Rusky your cat's problem is likely to be due to another aggressive or territorial cat in the neigbourhood.
Chances are the cat may have come into the house at night time and left its scent around table and chair legs and everything about 9" off the floor.
your cat is trying to put its own scent back into its territory and fearful of going out in case it meets up with this other cat.
Its essential your cat feels safe in your house (its territory) otherwise it will be very nervous and unstable.
Easiest answer is to either close the catflap at night and keep your cat in or put in a electronic catflap which reads your cats microchip number and only allows your cats in and out.
You'll also need to mask any possible scent traces with bleach . See if your cat does a lot off careful sniffing around the objects and walls in your kitchen which would indicate another animals scent.
rusky said:
We had a sudden behavior change in our cat a few months ago. She rarely uses the catflap & insists on us letting her out the front door.
She also started crapping & pissing in the house. Under our bed, on the kids beanbags, under the baby's cot, in the bath!!!!! Managed to kill one of the wife's orchids!
Not sure what triggered it, ma be another cat - I know that if we leave the catflap unlocked at night, one eats her food or the birth of number 2 child.