Corn Snake Opening Mouth Repeatedly?

Question
QUESTION: I bought a corn snake several years ago... about four years ago, I think, and I've seen him yawn occasionally, but I've never seen him do this. When I'm holding him, he'll open his mouth halfway repeatedly and kind of move backwards everytime he does it. His tongue also looks weird when he opens his mouth, but I can't quite describe it. He'll occasionally do it in his tank as well. Once he made a hissing noise that startled me, but I don't think he was hissing at me. He's been a very good and gentle snake since I first bought him. I don't think it has anything to do with aggression, since he hasn't bitten me yet (never has), but maybe I'm wrong.  

He has a bit of a food agression problem, because when I first bought him from a pet shop, they told me to feed him every two weeks to a month depending on the mouse size. They were wrong. I was told about a year ago that he was supposed to be fed every week and before that I was noticing weight loss. I've been feeding him once a week on a strict schedule up until a month ago, when I started a job. I've been having trouble keeping up with his schedule, I'm not sure if this has anything to do with it. I feed him frozen mice and he only had four tiny ones left, so I've been feeding him two mice, with the second being given a few minutes before the first.

We have an air conditioned house and he has a heating pad on. He just finished eating and shedding about a week and a half ago. He has no substrate in his tank, just newspaper. I'm afraid to put any in in case it's the problem for his weird mouth movements. It's cypress mulch, with a graph on the back of the bag stating that it was safe for certain snakes, such as corns.

The only reason I haven't taken him to a vet is that I can't locate a single vet in my area that handles snakes.

P.S -- Almost forgot. He's not wheezing, sneezing, blowing mucus bubbles, or anything like that. I googled the symptoms of respiratory infections and he doesn't have any of them. Same for mouth rot. His mouth doesn't look red to me, it's just pinkish.

ANSWER: I do not have an answer for the behavior, but I can tell you what is NOT wrong. You have done your homework and ruled out the two most likely serious issues. The other thing is that the snake is still eating. That rules out another big issue. I would not worry about the odd behavior. Let's look at the feeding issue.

You will get as many schools of thought on when and how to feed as their are keepers. I feed once every 2 weeks, a prey item equal to the biggest part of the snake (in girth). It seems to work well for everything from hognose snakes to pythons. Feed your snake when you can, but do not let him go over 3 weeks without offering food. If he refuses food, he can go about 1 month for every foot he is long before he gets into the danger zone.

---------- FOLLOW-UP ----------

QUESTION: Sorry to bother you again, but I picked him up just now to put him in his feeding box and he started doing that mouth thing again. This time, I noticed that the end of his tongue is real red. Is that a sign of mouth rot... is it just irritated or is that normal?

Answer
You are not bothering me, glad I can help. In my experience in snakes, the inside of the gums in front of and behind the teeth is noticeably inflamed if mouth rot is present. I don't think that the tongue is an indicator. If the snake is still eating, it is highly unlikely he has mouth rot. Here is a link to a trusted site on the subject:

http://www.peteducation.com/article.cfm?c=17+1831&aid=2385