Magical other world caused by gas leak and evil stone baby
Okay so I've been trying to find this for years and I may have some misrememberings or mixed up details. I believe I read it sometime between 2005-2015, but I never finished it. It was a thick novel, with a grey cover *I think*. It was about a boy who would travel back and forth to a magical other world, and I think I remember talking animals with red scarves who were a part of some secret order or like, heroes or librarians or something? Also there's a scene where it's revealed there's a gas leak in his home and the boy begins to doubt the magical other world is real. Also his mother was pregnant in the real world but loses the baby, and in the magical other world there's a scene where the baby is born, but he's like grey or made of stone and chases the main character? I think he also had a sword that had some kind of connection with colored gems? It was dark in tone and I didn't finish it as I was too young to understand a lot of it. I desperately want to read it now as an adult
Thank you all for your help in advance!
Edit: To add the gas leak detail