I've been out of town, that's why I haven't responded to this. Sounds like everybody is giving you good advice. I'll throw my two cents in too.
I have a king snake about the same age as yours. Mine loves to eat. I feed mine every week too. I feed her adult rats and quails. There are some pics of her somewhere on here of her eating a quail and then she came after me for desert, but that's another story.
Sometimes mine will refuse to eat for a month. No big deal, when she's ready I know she'll eat again.
I have one question for you. Do you feed live or frozen? I feed frozen. If I just drop the rat in she'll crawl to it, sometimes she'll strike and then eat it, but most of the time she'll act like it's not even there. I have to move the rat around to make her think it's alive. Sometimes she'll strike constrict and then lose interest. So to prevent that I hold the rat and pull on it after she strikes to make her think it's resisting.
So if you feed with frozen, you might want to try this. Be careful though, make sure you keep your hand out of her way.