Ugh, I went through a lot of stages...
Funny though, I remember that I was initially holding it also like Rambowjo, and in my left hand. My first computer mouse didn't have a scroll wheel back then -- yeah I'm really old -- instead it had three buttons, so it felt naturally to use it with three fingers.
Back then in school and in my family being a left handed kid was not very appreciated and my grandma constantly slapped my left hand if I used it for drawing! So I eventually was forced to become a right hander.
But when I got my first computer, I initially used the mouse with my left hand -- old habits.
However at school and anywhere else the mouses were always on the right side and I was too lazy to fumble with the mouse around putting it on the left.
When ergonomic mouses became more popular, and those were for right handers only of course, I definitely switched to the right hand. My hands kept growing and the mouses became more stylish and slimmer, there was simply not enough room for three fingers on top. Scrolling with the middle finger quickly felt weird, because my fingers became quite long.
So nowadays I use my mouse like a 'normal' person.
Two fingers, claw grip, index finger for scrolling, but thumb buttons on the side are still very important to me. My favorite mouse is Logitech's Revolution MX, best mouse ever made to fit my hand.