My alternative masturbation, does anyone else do this? Or am I unique?

When I was younger I used to do this weird thing where I would hang off tables, cross my legs and tense my vagina muscles. I don't know why I thought it was a good idea, but it made my muscles strong, including my stomach and arms. I've done it my whole life and never hid it, I did it everywhere. Recently I've realised that it's a type of masturbation... It really turns me on and makes me cum a ton! But it's also embarrassed me a bit because my whole family has seen me masturbate since I was around 5... Oops