It sounds as if your cat has tapeworms. The cat flea is part of the tapeworms life cycle & a source of infection. These worms can be transmitted to humans so if this was my cat I would get it down to the vet, PRONTO! Get the vet to explain the life cycle to you & administer the appropriate drugs because 'over the counter' remedies just won't do the job & therefore are a waste of money. Then you need to keep a diary of when your cat is wormed, flea treated & innoculated. Also when these things are next due, so that you can keep track of these essential healthcare jobs. It is much cheaper in the long run than waiting until you pet is ill enough to show symptoms.