I have a very stange compulsion: chewing on things. I don’t eat it, I just chew on it. Nails, pencils, even my shirts. Lots of times I just move it to my mouth without even realizing it. Right as I am typing, I found myself chewing a piece of plastic. Is there a technical term for this? Is there anything that cures it?
P.S. I searched on google for this, but I only found dog care sites. Can you believe this!?! DOG SITES! I am horribly insulted.
I’d recommend reading a book by Terra Ziporyn called Nameless Diseases.
Does this include sucking on things? Seems to be an oral fixation. I wish we lived closer.
Really, the only way to quit with something like that is to retrain oneself.
I have a jaw clenching problem & have found the best way to quit is to pay attention to what I’m doing with my mouth. If I catch myself clenching my jaw, I relax it straight away and remind myself to STAY relaxed. It isn’t a 100% immediate cure, but it has helped me with keeping my jaw more relaxed more often. Over time, I’ll get to a point where I don’t have to remind myself anymore.
For your chewing habit, try being concious of what you’re doing with your mouth. Whenever you catch yourself chewing on something, stop chewing right away and pay attention to the process of removing whatever item and placing it on the table, reminding yourself that you do not need to chew on things. As time goes by, you’ll likely be chewing less and having to replace fewer pencils. 
IANAPsychiatrist.
Sounds like a symptom of obsessive-compulsive disorder. If it’s really starting to interfere with having a normal life, a psychiatrist can prescribe Seratonin for you.