Probably his anal glands are blocked or something... it happens in male
cats and fat cats - the vet expresses (drains) the glands and
things should go back to normal. However, could also be
an abscess from a wound... Definitely need it checked out tho! Vet
visit would be best.
Everything they said. Anal glands. Need to be expressed. I hear it's pretty gross. and that you would want the vert to it expecially if you are grosses out easily. I have never personally seen it, but from the talk about it. I wouldnt want to.
Take him to the vet, that could most definatly be the problem.
To warn you, most cats I have seen will scream bloody murder when getting their anals expressed, so expect to hear that! I recommend they take kitty in back so you don't have to witness it, it can be hard on some owners who aren't used to it to see...