Loosing weight but eating like crazy

I’ve been meaning to take him to the vet soon as I’m growing more concerned, he vomited a few weeks ago i thought it was from eating so fast but now idk anymore, he’s been eating so many packs of wet food a day and not gaining weight, he is just always hungry so I’m not sure if he went through like a second puberty? But he’s 2 years old now and he used to be way more chonky. If anyone else has similar experiences I’d like to know!