18 week old cat poops outside the litter box sometimes?

[2blackkitties]

We recently got another cat. He is about 18 weeks old now. We notice that he doesn't always poop in the litter box. I know he knows how to use it and where it is since he uses it most of the time, but why does he not use it sometimes? 
Also, is it normal for his stomach to make gurgling sounds? I plan to take him to the vet soon, but I figured I would ask here anyway, too. 

 

[vball91]

Do you only have the one litter box? If so, I would definitely try adding at least one more. Some cats don't like to poop where they pee. Also, you may try scooping more frequently as some cats don't like a dirty box.

It is not normal for a cat's stomach to make gurgling sounds, so it's good you're taking him to the vet to get checked out.

 

[2blackkitties]

Do you only have the one litter box? If so, I would definitely try adding at least one more. Some cats don't like to poop where they pee. Also, you may try scooping more frequently as some cats don't like a dirty box.

It is not normal for a cat's stomach to make gurgling sounds, so it's good you're taking him to the vet to get checked out.

Yeah, just one box. I'm not sure where to put another one. I'll have to find a spot. It seems to have resolved, though. I haven't noticed his poop anywhere else. 
Could it have been that I used new litter? I added half new to the old until I could afford to get the regular litter that we get.