Is it normal i like it to scratch or roll the knot of thread

i use to scratch or roll the thread knot by my thumb and index finger i still like to do it. i dont know why i like it. Most of my shirt buttons thread knot are lossen up coz of this habbit.more the knots make the thread sharper which i like to roll or pinch and scratch with my thumb and index finger is it normal i use to do this since i was of 5 years old.