Likely you are only stimulating a small portion of the penis with your mouth which is not enough to get him off...or if you are it is too hard on your jaw and lips (aka cocksucker's cramp). Therefore, you should make the penis really wet and use both your one hand at the base of the penis and your lips at the top of the penis in order to exert enough pressure to cause an ejaculation. Hope this helps...nothing worse then chafed lips, a locked jaw and no jism.
I swallow
-dirt dobbler