Why won't my snake eat?

I found an Eastern Hognosed Snake in my back yard just over three weeks ago. I have always loved snakes, so I decided to keep him. He is only about a foot long and pretty thin still. When I found him, he had just eaten a toad that was too big for him, and had a nice lump for about a week. Since I've had him, he hasn't eaten anything. I've tried toads, tree frogs, crickets, and a fully thawed pinky that was split brained and one that was covered in toad blood. He isn't getting aggressive or showing any signs of hunger that I know of, but I'm getting scared that he is hungry. I don't know if I need to wait, try something else, or if I need to let him go, which I really won't want to do. Please help me!!