Does anyone know what could be wrong with my cat?

i have a long haired cat thats only about a yr old and stays inside. for about a week now he's been meowing really weird. he doesnt look like hes in pain and still plays but his meow sounds like hes running out of batteries or something (not sure how else to describe it lol). he also spits sometimes but has done that since i got him and may be cuz he drinks a lot of water. i wasnt brushing him everyday cuz he didnt look like he needed it, but i got worried that maybe he has a bad hairball so i brushed him the other day and got a ton of hair, so now im brushing him every night. im not sure if the problem is a hairball or something else, maybe someone here might have some ideas? i saw online that using a small amount of melted butter can help but i want to make sure its safe and wont hurt him first. i dont have enough money to get medicine for him until june 7th so if it can wait till then i can get stuff, but if it needs to be dealt with right away would the butter be ok for him?