My cat is still throwing up. What should I do?

My cat Spike (8 years) has been throwing up since Saturday Morning. (he has thrown up since then on Sunday, Monday, Tuesday, Thursday and today Friday) So everyday but Wednesday. I took him to the vet Monday they did blood work and a stool sample. Everything came out fine. So I switched his food to Royal Canin Special 33 for sensitive stomach. I did this yesterday and I also received medicine from the vet Metronidazole and cat lax for hairballs. He throws up about 10 hours after eating and I can still see most of his food in his puke. I don’t know what else to do. He acts normal and everything but I dont know why he is throwing up so much I only feed him a tiny scoop of food 2x a day and yes he eats fast but I split up his portions. Can someone please give me some advice on what I should do? I’m really worried Spike means everything to me.