My wife thinks I'm odd

Now, this isn't news, of course, but it's why she said that I'm odd recently. Over the past few months I've been biting the inside of my lip. It's kind of a compulsion. This happens to me every once in a while - the inside of my lip becomes dryer and, well, biteable. I don't know why it happens; it doesn't seem to coincide with any kind of temperature, but it happens occasionally. When it does, I feel the need to bite my lip. I don't like to do it, but like I said, it's kind of a compulsion. It doesn't hurt at all, and it doesn't seem to cause any long-term damage to the inside of my lip. Then, last week, something happened and the inside of my lip is no longer that dry and therefore no longer biteable. In fact, I doubt if I could bite it without doing some damage. Again, I have no idea why this happens. Does my body chemistry change? Is it because of the weather? The temperature rose last week to triple digits, but then it went back down. It's still hot, but not the ridiculous heat we'll get later in the summer. Anyway, I'm not biting the inside of my lip anymore. Any ideas what happened?

This isn't a big physiological problem, but I find it interesting. I made the mistake of mentioning it to my lovely wife, who called me "odd." This is why my wife and I never speak to each other. It's best if we don't know what's going on in each others' minds.