Definitely this is a vet trip needing to happen.
The fact he is defecating on the floor suggests that his urethra may be partially blocked, this is common in young male cats. The idea is he needs to pee and strains...
My cat keeps weeing on the sofa! We have had him about 8/9 months now and he is going in and out the cat flap fine in the day. However sometimes when we get home or wale ip in the morning there is cat wee on the sofa. At first we thought it was because the litter tray was dirty but now he has 2 by the back door where the cat flap is and another one outside in the garden so there's no excuse. He has done it maybe about 10 times since we've had him and we wash it with detergent so there is no need for the smell to remain. Please please can someone help because otherwise my boyfriend keeps saying we will have to get rid of him!as we have had him for 8/9 months and he has done it that many time I don't think it could be UTI! Help! Please.
Well, If you had asked this question in a couple months, I may have a better answer for you.
But, I AM in the process of toilet training (For a human toilet) my two cats, ages 3 years and 5 years. The older is a girl, the younger is a boy, both fixed from 6 months or so old.
They are doing really well.. An adult cat CAN BE TRAINED to use the toilet.
Basically, you buy something called "Cat Training" and follow the steps on this website. My cats really seem to be doing okay. I think they'll take to it. But I'm going SLOW.. With an adult you have to go slower than with a kitten. BUT something to keep in mind, for at least a few weeks you WILL have to use a normal litter box. Changes have to be made gradually, step by step. Here's the websites.
Or you can just show her where the toilet is. I've found that technique to work in the past with litter boxes so a toilet should be no different. Just set her down on the seat. She will take it from there.
All About Cats http://cats.about.com/
Video Lessons http://www.expertvillage.com/video/157785_toilet-train-cat.htm
Cat Toilet Training http://cattrainingsecrets.net/toilettrainmycatreviewscam/
The "accidents" are his way of telling you something. I would first take him to a vet to rule out physical causes like urinary tract infections. If it is emotional, it could trace back to a change in environment. There is a good article in our health pages entitled "litter box issues - environmental" which I recommend that you read. You will find the health pages on the lower right of the page you are on right now. Just go in and click on that title.
The aggressive behavior is probably mostly youth. Young cats can seem distressingly aggressive and sort of unsettled even though they can also be very sweet and cuddly. Normal and he will grow out of that. Some of it could also be a reaction to an environmental change, just like an emotional litter box reaction talked about in the health page article.
Barring a physical cause, you will need patience and time. No scolding or punishing, you will only cause confusion and hostility that way.
In the meantime, Nature's Miracle will get rid of the smell (nothing else works in my experience). You can get it at most pet stores - just follow the directions exactly.
And yes, if he isn't neutered, it would be an excellent idea to make an appointment for that, ASAP! It will calm him down quite a bit, keep him from spraying (which is a habit that can't be addressed like litter box issues can) and it is better for his health and happiness.
Good luck! Come back with any other concerns or questions, anytime.