Little one

I really need help with my little one, he is refusing to eat and drink, he used to love his breakfast but now a normal 15 minutes eating breakfast can take upto 2 hours, and him shouting and chucking his food. The health Visitor have been amazing and given me ideas on what to do but he now point blank refusing food and drink. I just dont know what to do anymore feels like I've hit a brick wall and it really getting me down as he always used to eat. Any advice would be gratefully appreciated