Reptile & Amphibian Forums

I am at a loss here. Yesterday morning, and this morning also, my cat crapped on the floor. I have had Inky, a male am. shorthair, since last november (got him from the spca) and he never had done anything like this. It seems like he is just standing there, and you'll look and the crap is actually sticking out of him, but he stands there and acts like he doesn't know he has to go.
Maybe this is a bid for attention? We are not home for about 9 hours of the day. I thought of getting him a companion cat, but we tried a few months back, and he attacked the cat we were trying to adopt.
His litter box is always very clean, so that can't be the problem. It is however kind of in an "out of the way" location. But again, it does not seem like he knew he had to go; he was just running madly around the house and it would come out of him. Please help me, I am very repelled by my little guy, and I love this kitty and want to resolve this!
I should add, he has a habit of peeing on plastic bags if they are left around the hallway or in a closet on the floor. Why does he do this? I should add, he is an indoor cat, but he constantly tries getting outside, think he was indoor/out in his last home. THANKS for any advice you can give util his vet appointment next week!

Inky is slightly overweight. Not too fat, but a bit pudgy. He had worms back when we first got him, but was dewormed with pills. Coiuld this be a symptom of recurring worms? we're going to the vet next week.