LTHan

So I have an old corn snake, fifteen or sixteen years old. He's always been super food focused, his first reaction to any movement in his enclosure was to try and eat it, but otherwise is a super good natured snake, I don't think I've ever seen him aggressive.

Recently he's been having increasing trouble with food. At first he seemed a lot more tentative and unsure about his food. Then, he'd regurgitate the mouse if anything disturbed him before he'd completely swallowed it, so I'd have to turn off the lights and leave the room for him to eat.

Now, for the last four or five weeks he's not eating at all, at the last two time I've tried he reacts aggressively/fearfully to the mouse. I've left mice in overnight, and tried smaller sizes. I'm also unsure if he's drinking, I haven't seen him do so in a while. His mouth seems pink and healthy. He's starting to get skinny, so I'm getting worried. Any advice would be very much appreciated.