Gorren, this cat is continually defecating in your room because no matter what you do, that's where it has formed it's habit now, and that's where it smells its own scent. Even though you may not be able to smell it after you've cleaned it, this kitty can.
You can buy a product that will eliminate the odour to your nose AND the kitty's, and then I suggest that you put a litter tray in your room. This does not have to be permanent, but this cat is going to continue to use your room as a toilet because it has got into this habit, and cats are creatures of habit and they will stick to something once they're happy with it.
You need to retrain this kitty to go in a litter tray, to start with, and that is going to have to be in your room. As time goes by, you start moving the tray nearer and nearer to the door, as long as the cat keep using it. Eventually (and it won't take that long) you will be able to move the tray out of the room entirely and the cat will have formed a NEW habit - which is going in the tray and not your room.
You need to get the cat neutered, very soon, because if you don't having it pee and poop in your room is going to be the least of your concerns.
Does he have a litter tray that he can use anyway? If so, put it in your room. Get some Feliway spray and spray it on the areas where he used to poop after you have cleaned them with a proper cleaner. Feliway diffusers help calm cats, Feliway sprays keep them away from things they're not supposed to be on. Put a tray in your room and keep it clean.
If you do these things your problem will end - but remember cats dislike change so it will take a couple of months. It will be worth it in the end, though.