For about a year now I have had a loud pop occur when I go from having my neck flexed with chin up to bringing chin down closer to my chest. No pain whatsoever, but it is loud (others look at me and say "WHAT WAS THAT!!?!" and it frightens me because it feels like my head is going to break off. I know that sounds quite peculiar, but it is the best way I can describe it. It continues to get more pronounced as the months wear on. I can go through periods where it doesn't happen at all, and then through periods where it happens 20 times a day. I can never tell when it will pop, so it has me on edge too. Any idea what this could be?