I've Had 3 Scans Of My Head Within The Past

I've had 3 scans of my head within the past 8 years, haven't had one in 2 years. I can't get rid of my headaches/neck aches. It feels like there is a knot on the left side of my head above my ear. I do have TMJ but have a night guard. Is there any possible way they're missing a tumor or something serious??