You do Samten. You might like to take a look at the videos on
www.knittinghelp.com, they'll show you how to use circulars.
Do you knit with the yarn in your left or your right hand? I knit with the yarn in my right hand and sort of balance the circular needle against my thumb to steady it while I flick the yarn round it with my index finger. I'll try and get a photo taken of how I hold my needles. I got shown how to do it one day when I was sitting in a hospital waiting room and an older lady saw me struggling with my circular needle and showed me an easier way. I tried it and it worked.
I also hold my needles under the palm of my hand, not over my hand like a pencil as I've seen in the knitting videos! This is probably because I was taught by my great aunt who held her long straight needles from under her hands with the knobs tucked under her elbows. Gives you a lot more control than letting go of the needle each time you make a stitch.