So I am leaving Jan 1, super late flight. Coming home Jan 4, super late flight. Chicago to Las Vegas, and vice versa. Basically, I'll be wearing the same jeans the entire time. Don't need to pack much. A hoodie will be worn. I will pack a couple underwear. Any other essentials I may need, I'll just grab at CVS. Basically, I want to bring a drawstring backpack. A small one. Nothing big. I did not check in a bag with Frontier. They said a small personal item is free. Does my bag qualify, especially if I don't pack much in it other than a couple underwear and socks?