Thank you,I am glad to see that he has no discomfort and is eating/drinking for you. Still I would note that if you think he is drinking a lot more then usual (more then you'd expect with his being on the dry diet), then we'd need to be wary of that since it can be a sign of health issues (ie metabolic diseases like diabetes
or issues with the thyroid or also a hint of early stage organ troubles). Now that all aside, I do want to mention some options that we can use to just facilitate getting him passing feces since this has been going on too long for a cat who isn't off his food.
First, you can offer some cow milk. Kitties are like little lactose intolerant people, and while the love milk it can move things down the gut a bit quicker (ie. Cause mild diarrhea
in an unconstipated cat). If he is mildly constipated, this might just get things moving in the right direction. You can also treat them with hairball medication (ie. Catalax, Laxatone, etc). This is available from the vet or the pet shop. It works to lubricate the gut and can facilitate the movement of hard feces out of the rectum. . Alternatively, you can administer a small volume of Miralax (1 tsp per 24 hours), lactulose or mineral oil orally (ideally offer in wet food or if given via oral syringe then take care to avoid aspiration, since that would cause problems we'd best avoid) as a GI lubricant. Furthermore, if he is eating you and will accept wet food, then you can mix in some canned pumpkin or a 1/4 teaspoon of unflavored Metamucil. Just like people, these can restore fecal output regularity. I would offer these with wet food to ease him eating of it, while making sure we are getting water into him (as canned food is 35% water). Overall, I share your concern for the duration of his lack of feces. It is positive that he is comfortable and eating but we do need to make sure that he is passing stool regularly. Therefore, it is ideal that he has a check up today, but I would note that you can try the above in the meantime to see if you can get him to pass some stool. Of course, if he still does not, they his vet can have a feel of him to diagnose constipation +/- give him an enema to clear him out if needed. Please take care,Dr. B.