If you are worried I suggest you make an appointment to see the vet for consultation. For long discussion with my vet I would usually make an appointment so that he will have that extra time for consultation. Especially when I need some advice on my cats' behaviour.

Simba pissing around? Most probably normal since he is a boy and if not yet neutered he will start marking in new place. Even if neutered but the neutering was late, i.e. when he learn to mark before, he will do the same.

Simba vomiting - not so good unless it was hairball, but I am sure you have been informed on this before. Worm perhaps? just a thought since he also had a bout of diarrhoes.

Not eating, could it be because of different kinds of food? Or could it be because of gastroenteritis (food poisoning)? Or could it be because of worms? Try deworming again.

Simba sleeps a lot. It might be because he was having diarrhoea and vomiting that he is slightly dehydrated?

Still suggest meeting the vet though. They know best.

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