I’m at a loss

Ladies I need some help. My son is now three weeks old and he seems to constantly be hungry. He will eat about two and a half ounces every feeding, he will spit up everything if he eats more than that. He seems to be hungry again less than an hour later. I don’t understand why he seems so hungry. It’s keeping him awake at night which means I haven’t been sleeping either. I am exhausted running on about six or so hours of sleep in two days. Can someone please give me advice on how to make him go longer between feeds? This is my first kid if anyone wants to know.