I am an 18 year old, circumcised male. My penis already has keratinized. However, I feel as though my glans have recently become more dry and less sensitive. I have no condition that could cause this loss of sensitivity. I am healthy and not obese. I exercise daily as well. Is there a way to "de-keratinize" a penis? Or at least a way to restore sensitivity back to my glans?
Also, I have been ejaculating a certain way, and I to make sure it's not harmful. I contract my penile muscles, almost like doing kegel exercises. I do extreme contractions, then a lot of smaller contractions. I do not use stimulation by touch or thoughts or porn. However, I do rub my penis to get the initial erection or when my penis starts to go flaccid. Anyway, I do these extreme contractions until I orgasm, although it's not quite pleasurable, I do ejaculate more than I would regularly. Is this dangerous for my prostrate, since I'm contracting those muscles for such a long period of time? I have noticed a positive affect. I have harder erections and my erections last longer.
"Keratinized" refers to the process in which our skin forms a layer of protein that protects our skin. Keratin forms the outermost layer of our skin. Actually there are dozens of different types of keratin in the human body -- some are hard (like your nails) and some soft. Everyone, circumcised or not, has keratin on the outer layer of their glans.
An uncircumcised male has a foreskin that both protects the glans and keeps it lubricated with oils until an erection causes it to be exposed. It is the oils that keep the surface flexible. Being protected most of the time also makes it more sensitive to touch. Every once in a while I get notes from uncircumcised boys who find erections painful because their sensitivity is so high. A circumcised male's glans takes on a color more close to the rest of his skin because there is less oil in it (well oiled skin is more transparent). The nerve endings remain the same in the glans, circumcised or not, but a circumcised male is more used to his glans being touched and so his brain filters out the feedback. This does not translate into being less sensitive in other ways. A recent Canadian study concluded that the glans remains similarly sensitive, whether you are circumcised or not.
What does change is the lack of the foreskin, which does have its own nerve endings and can be more sensitive than even a man's glans. But you can't get back your foreskin with its nerve endings after it has been removed.
If you want, you can put lotion on your glans to increase the softness of the skin there, but it won't make a huge difference.
Generally the warning with Kegel exercises is to not continually do them while urinating because it can cause the bladder not to completely empty itself. Basically, what you are describing is that you have figured out a way to use your interior muscles to massage your prostate enough to trigger an orgasm. As long as you are able to relax those same muscles so that they don't interfere with urinating or ejaculating, then it won't be a problem -- and it sounds like you are able to relax them enough at the proper times.