I am pretty new to minecraft, I started playing about 2 weeks before 1.8 was released. I am having a problem now where monsters spawn in my house when I am awake and working on other parts of my house. I have no problem sleeping, I don't get monsters then. I might be down a level working on a basement and then come up the stairs to find a two creepers on the way down to say hello. The last time it happened, they spawn on the top level of my house (which was 3 levels) I went through and made sure all the walls were 2x thick and had plenty of lighting. I am not sure if this was a bug but it started happening after the 1.8 updates.