Why are you giving him antibiotics? It takes a toll on their tiny bodies and if was just a hibernation attempt, then you not accomplishing anything by giving him antibiotics.
I doubt your house is all above 75. He may have gotten too cold at some point when running around and attempted hibernation or he was cold even before that, in his cage.
You need to make sure more or less the whole cage is heated to the same temperature, try to insulate it with foam insulation or coroplast, or even just blankets but leave some space for the air to circulate. Make sure where ever he sleeps is warm enough. I put my hedgehog in a sleeping sack for the day that I wrap another fleece around, and place it under a CHE.
You just got him two weeks ago, and he's attempted hibernation. That tells me you need to be more vigilant with your hedgehog. Remember, his back is covered with quills. They do not provide any insulation. That is why they will get cold easily.