Infinity enchantment not working.

I recently made an enchanting table with 15 bookshelves which required a lot of work. But I managed to do it😁. But when I enchanted my bow with infinity, it still required arrows. I was so disappointed 😔. I killed like a hundred sheep and cows. All those animals sacrificed to do nothing. It just stole my 3 lapis lazuli and experience level. Please fix this.