Masturbation question

Hi! Im a woman 20 years old and i have a question for my fellow girls, i have this thing ive done sense i was VERY very little and ive never been able to find any info on it to know what it is even is; i want to know if its something negative or normal. Ever sense i was SUPER young like 7 years old, ive done this thing my parents called it “scruntching” where i get on like the corner of my bed or wherever, i put on leg under the other kind of sitting on my knees, and i kind of bounce up and down, it feels like a form of masturbation, and when i do it eventually i get to a point where i feel like i cum, however im not even touching myself, when i was small i would do it IN THE OPEN, and my mom would ask if my stomach was hurting so thats why i wonder if its something i should consult my docter with? Idk. The reason i ask is because sometimes i get the urge to do it when im home alone and ill sit there for 30 mins at a time not being able to stop. Im 20 with a boyfriend who i have amazing sex with, idk why this still consumes me