What is happening to my brain?

I'll think about something and it gives a domino effect and then I start to get nervous and I will do little things to feel better (ie. shake my leg, pace and touch all the bricks on the wall, touch my hand to my head and back to the chair in a rapid motion.) And if I don't do these things my brain starts to scream and I will look completely fine and inside I am screaming at the top of my lungs. I feel like doing these things releases the bad thoughts and music also helps but it is just one song "Under Pressure" by David Bowie and Queen and singing to it makes me feel better and I have like visions of me being on a stage singing they make me feel better also.