I'm sorry to hear that you're having problems. I've only had this problem with my cat Starr and he has colitis and food allergies that cause him to sometimes have diarrhea and mushy poos so he sometimes can't make it to the litterboxes in time. I agree that you should take your cat to the vet for a check up.

I've found that my cats prefer open litterboxes instead of the ones with the hoods on them. I buy ex-large/jumbo litterboxes that have high sides to them so they can't kick litter every where or pee over the top of them. I've also been putting cat attract litter on top of the regular litter that I use and my cats seem to like this a lot. You can buy it online or at Petsmart.

How old is your litterbox? If the litterbox is very old then sometimes this will also be a reason for a cat not using the box. They can become sratched up and just smell bad to your cat. I also cleaned all of my older boxes with soap and water and now my cats have been using them much more. Good luck.