When kitties drag their bottom on the floor, it can be due to a few differenti issues. We can see this when cats have tapeworms, impacted anal glands, and with constipation when they cannot pass all the feces they are trying to pass.
If he hasn't been wormed recently, consider doing so now. You can get good quality wormers (ie. Drontal) from either your vet or pet store.
You can also treat them with hairball medication (ie. Catalax). 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.
Furthermore, if he is eating you can mix in some canned pumpkin or a 1/4t 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).
I would also encourage them to drink as constipation can be complicated by dehydration. Make sure they have fresh water and you can even offer low sodium chicken broth if they won’t drink.
While you are doing this, I would advise that you monitor fecal and urinary output. I would advise trying the above measures, but if you aren't seeing feces in the next 24-48 hours, or your cat begins to vomit or worsens, then they should be evaluated by a vet.Severe impactions of feces are usually secondary to more serious diseases, so if he doesn't respond to our gentle colon cleaning treatments, then he may require more aggressive treatment (ie enemas under sedation). As well, if he doesn't settle and is still dragging his bottom despite your treatments, then have the vet check his anal glands (and express them if necessary).
Please let me know if you have any further questions. If you have no further questions, I would be grateful if you would press the wee green accept. Thank you, Dr. B.