Hi,
What about "it" doesn't work? This sentence seems to indicate that the act(ions) are somehow not happening correctly. Your second statement indicates that you are experiencing a problem with the act when on top. I'm gonna go with the second, first; and the first, second.

How are things in general and with using other positions?

The Woman Superior position is fantastic for women because it places them in a dominent posture AND gives them complete control over:
* Angle of penetration
* Speed of penetration
* Depth of penetration
* Rhythm of stroking
* Length of strokes
* Speed
* Their own level of arousal

with benefits:
* Toying with their man's arousal
* Different visual perspective
* Different feel

Have you looked at the situation in this way?

How do you analyze the problem? Can you give us more information on what seems to be or not to be happening either physically or mentally?

Does your man continue to caress and fondle you? Does he have the difficulty rather than you?

I look forward to having more information on which to conjure up an opinion.

> i cant seem to get the rythm right, i start moving up and down and then freeze. i feel stupid and end up just rolling back onto the bed so he can go on top.

Oh, well, if this is all it is then I'd say it's not big deal, just experiement and try different postures, for example:
* Squat
* Kneel
* Lean forward on your hands or forearms

Rather than use one of these, try one or both of the other two.

* Sit on him and gyrate your bottom in a back and forth or side to side motion rather than raising and lowering your body to do stroking.

Let him know you are having trouble finding and maintaining a rhythm and ask him to be patient and to give you feedback on what you do that works for him.

If you are concerned about not getting the right stimulation for yourself, then position yourself so that your pieces-parts rub against his pubic bone--or experiment and see what else works for you.

This position is great for women, however, some guys find that they have a difficult time climaxing in this position. If this is the case with your lover, then you may just have to be selfish and use it for your pleasure and then afterward, pleasure him in another way or position.

> i start moving up and down and then freeze.

You probably just have to work at it, prolonging the movements that seem to work a little bit each time, or, take a rest break now and then and then continue one trying to extend the time you go before having to take another break. Put another way, your muscles just may require some training in order to learn new movments and not tire.

Comments?

> i dont want him 2 get bored of me

I rather doubt he will become bored if you keep him aroused and excited in other ways while you are working out on top of him trying to reach your climax. If he cannot reach his using this position then keep him amused in other ways either at the same time or afterwards.