It is not a brain tumor, and you are goign to be fine. Your OCD is focusing on your mouth/jaw for whatever reason. The more you try to repress these feelings without dealing with them, it will only reinforce the irrational fears. I know it hard to deal with, and I'm not a doctor, so I don't have much advice, but with my former OCD symptoms, I had to FORCE myself over years to recognize that these fears were irrational and then keep doing the activity that scared me--face it head on while telling yourself over and over that you are going to be okay and the compulsions are not necessary. I had fears of writing letters the wrong way, and I was afraid that the letters would come alive and kill me. I forced myself to say, "this is not rational, paper isn't alive" and when I would write the letter incorrectly (to my standards), I would leave it alone. I wouldn't change it like I used to (i would spend houuuuurrrss rewriting assignments).