ConfusedGirl, When you say 'i cant feel anything', do you mean you do not orgasm or you do not feel anything? Do you orgasm in other positions?
When you are on top, you are driving intercourse. You will have to find the angle, depth and motion that will get you the stimulation you need.
If you are orgasming from other positions, do you do so from clitoral stimulation, or from your vagina? Normally a woman will orgasm from clitoral stimulation. If you sit too upright when you are on top, your clitoris will not get the stimulation it needs. You can lean forwards dropping your upper body on his. You (or him) can rub your clitoris during intercourse or you can change your action from up/down to rubbing/sliding forwards and backwards. Whatever you do, when you are on top, you are in charge and need to look after your needs.
Your other option is to do the on top to give him the visual and mental stimulation it brings to him but stop short of him ejaculating, and then swap around so that you can finish in a position that works for you. You can even swap back to being on top to finish him once you had your orgasm.
You should also try to extend the amount of time you have intercourse. The length of penis-in-vagina time is directly related to your orgasm. This is often difficult when you are on top or in doggie as these are very stimulating for him.
Best of luck!