Can it be that you are expecting orgasms to be something different than what they actually are? It might sound stupid, but since you are not born with the knowledge of what an orgasm feels like, some women are searching for something more, and think they are not experiencing orgasms when they actually do.
Sexual arousal is the build up of muscle tension in your pelvis and hands to the point where it can become frustrating to you. This is accompanied by an increased heart rate and breathing.
An orgasm is the sudden release of this tension in a number of very pleasurable waves of muscle contractions in your genitals, accompanied by possible heat waves radiating out from your genitals (often your uterus). This is aloso normally accompanied by involuntary muscle contractions.
So arousal is the gathering of all this energy inwards, orgasm is the expulsion of this energy outwards.
When you masturbate, what do you experience? When and why do you stop?