If you want a quick fix, pull back your foreskin and leave it retracted 24/7 for about two weeks. At first it'll feel really uncomfortable rubbing against your underwear, but after about the first week it'll be tolerable, and by the end of the second you'll be pretty much used to it. It's an effective means to reduce some of the hypersensitivity. If you want to go further you can leave it even longer.
It's something I did a few years ago and the outcome has been really positive. My dick is more versatile now and I can use it in different ways without worrying about hurting the head, and it's especially useful if you have a partner who's a bit rough with it.