Too sensitive during orgasm!

This may be TMI, but I have a question for you all. I have noticed that when I start to orgasm, the head of my penis gets painfully sensitive. It gets so sensitive that it's uncomfortable to even have anything touching it during orgasm. I know that it is normal for this to happen after orgasm, but does it usually happen right when the orgasm starts?

Also, is there anything I can do to prevent myself from getting quite so sensitive? I have heard that if you can keep stimulating the tip during orgasm it can make for an amazing experience, but with my sensitivity as it is now extra stimulation does nothing but mess up my orgasm. I know that there are desensitizing creams and such, but I really don't want to become less sensitive overall, just less sensitive at that one moment lol.

Thanks for the advice.