I am sorry to hear you are worried about Oreo. My name is Rebecca. I am a veterinarian and will do my best to help.
Is he having trouble urinating, or is he urinating normally? How do you know he is looking for a place to defecate rather than urinate?
I ask because male cats sometimes get a blockage in the penis, and they can't urinate. They will try over and over to urinate, moving from place to place, straining and posturing like they are trying to go, but nothing coming out. If he has this problem, it is usually an emergency. If a cat goes too long without passing urine, they go into kidney failure.
If he is urinating normally, but is straining to pass stool, he may be constipated. Is he eating? If he is eating, you can try adding stool softeners to his food like Mira Lax (1/4th teaspoon twice daily). If he is not eating, or if he is vomiting, he may need to see a veterinarian for manual extraction of feces, and/or enemas. There are no safe over the counter enemas made for people that are safe in dogs.
Let me know if he is doing, and what other questions you have.