If you are afraid of commitment, you might pick someone that might reject you so you have a sense of control. That might be hard on your ego though. Have some friends fix you up. You might also view yourself as damaged goods, so you feel you must always aim low. If that is the case, get some help to boost your self-esteem.
Some women have very quiet orgasms.
Some women may be fearful of looking unfeminine as they wail and grimace during orgasm, or their orgasm is so subtle that a man can't tell. You might want to ask if she is reaching orgasm or if there is something you can do to make it better. If she is having problems having orgasms, don't make it your ultimate goal to make her have one. Let her invite you to participate in making it better. If she feels pressure to have one, that will make it worse.