I can tell you this from experience, you're not inhailing it right. I toked for about 6-10 times before I ever got high, and when I did, well the cops brought me down but that's a different story...

Anyways, you should use a gravity bong, that will surly get you high, it is made to make you take in a HUGE hit with lots of air, try to breathe out most of your oxygen before you take a hit. Keep trying, I had the same problem, I watched my friends smoke cancer sticks, I told myself I should suck that bong rip down into my lungs... That night was my first time getting high