I'm an animal health technician so I can maybe help. If you think he has a blockage (urinary blockage) go to the vet RIGHT NOW. That condition is extremely urgent and he needs veterinary help right away.
Signs of blockage can be: -difficulty to urinate, urinating outside of litterbox, less active, painful abdomen because the bladder is distended.
If it's just diarrhea and vomitting, it might be because of the worms. To get rid of a big worm infestation, he need deworming medication for a couple of months and monthly analysis of his feces which can be done at your vet clinic. For the diarrhea you might want to try a gastrointestinal diet that can be bought at any vet clinic. It really works.
If you have any doubts, you can always call your vet clinic and they'll be happy to answer your questions or give you an appointment.