Try not to masterbate for awhile, and see if some of that sensitivity comes back.
You could also look into the following herbs, they are excellent for male sexuality.
Maca (lepidium meyenii) - is a plant grown in Peru that produces a radish-like root that is responsible for its sex-enhancing ability. In studies, subjects given maca experienced greater sexual satisfaction, increased energy, and stamina. This plant has long been used to restore sexual vitality, enjoyment and performance.
L-Arginine - is an crystalline, free-form amino acid that has been show to improve erections, while at the same time benefiting cardiac blood vessel reactivity. It is also an important factor in muscle metabolism and aids in transportation, storage and disposal of nitrogen throughout the body.
Oatstraw (avena sativa) - this restorative herb assists in renewing and strengthening the vitality of the nervous system as well as restoring elasticity to veins and improving circulatory functions. Other noted benefits of Oatstraw are increased balance, memory, sensitivity to pleasant stimuli, and improved coordination.
Ginseng blend (Siberian, American, Korean) - has long been used traditionally as a stimulant to deliver extra energy. It is also well know for its aphrodisiac effects. This herb has been demonstrated to combat impotence, infertility and premature ejaculation. In addition it also normalizes blood pressure while revitalizing the body and promoting the growth of nerve tissue. Additionally, Ginseng contains the key ingredient ginsenoside, which alters the blood flow to the brain and penis it also increases sperm production.
Catuaba (bark extract, 4:1) - native to brazil and parts of the Amazon, catuaba is a central nervous system stimulant commonly used throughout the world for treating sexual impotence, exhaustion and fatigue.
Muira Pauma (ptychopetalum olacoides) - the root of this shrub, native to Brazil, has been proven in a sexology study in Paris, France to increases libido as well as helps patients with erectile dysfunction (ED). In fact, preliminary research suggests that Muira Pauma is one of the best botanical remedies for erectile dysfunction and increased blood flow to the penis.
Oyster Meat - since the Roman Empire these creatures have enjoyed a risqué reputation. Well know for their aphrodisiac qualities in both men and women alike, oysters aid in both sperm and testosterone production in men as well as increased libido and sex drive.
Nettle leaf (urtica dioica) - has a long documented history from ancient Greece to present. The polysaccharides (complex sugars) and lectins (large protein-sugar molecules are the active constituents of this plant. They directly affect the hormones and proteins that support sex hormones (such as testosterone and estrogen) within the body. This has been confirmed in double blind studies.
Orchid Substance - has long been known to create an aphrodisiac effect in both men and women. This herb is used for its strong qualities that promote and encourage sexual motivation. The increase in libido due to consuming this plant is unlike any other.
Tribulus (tribulus terrestris) - this Indian herb restores and improves libido, it also prolongs the duration of an erection. It is very popular for its dominate role in supporting the reproductive functions of men. Additionally, it increases anabolic hormones and testosterone to optimum levels as well as increasing sex drive.
Cayenne (capsicum frutescens) - has been used in India for decades for its powerful stimulant effects. Additionally, this plant helps to dilate blood vessels, thus leading to harder more attainable erections. This plant is another must for any man wanting to maximize his sexual performance.
Zinc Oxide - an essential component of more than 300 enzymes needed to maintain fertility and normal testosterone levels in adult men. It also is known to have beneficial effects on cardiac blood vessel reactivity.
Astragalus (astragalus membranceous) - the roots of this plant are harvested in northern China and Mongolia. Astragalus is known for it's normalizing effects on the body's functions. Modern research confirms it also supports immune defenses.
Sarsaparilla (smilax officinalis) - is a vine native to tropical America and the West Indies. The roots are unearthed and harvested throughout the year and are used to aid in testosterone activity in the body.
Boron (citrate) - this mineral is vital for proper male nutrition as well as maintaining proper blood levels of estradiol, which is a precursor of estrogen. Estrogen is a sex hormone that must be regulated to insure maximum male sexual performance.
Pumpkin (cucurbita pepo) - has been scientifically proven to have positive effects on one's health. Pumpkin seed promotes male potency, is an effective prevention of heart and circulatory diseases, and lowers cholesterol levels.
Licorice (glycyrrhizzin glabra) - this powdered root is useful in pill-making because of its absorbent qualities, being used to impart stiffness to pill masses and increase proper absorption.
Those ingredients are proven to increase male stamina, vitality and erection quality.