"masturbation will assist in making it less sensitive, but more comfortable over time." *i meant masturbating with your head exposed*
What you need to do is take time everyday to stretch your foreskin so that it can be easily retracted and moved back over the head of your penis with ease. Do it in the shower as the warm water/environment softens the skin and makes it more elastic and therefore can assist in being able to loosen your foreskin. You can also google other stretching techniques online to assist you.
Your penis head is so sensitve because it hasn't seen the light of day that much and is so sensitive that it does make it uncomfortable when exposed. When your able to fully retract your foreskin, masturbation will assist in making it less sensitive, but more confortable over time (especially when ejaculating) and the pain will turn to pleasure (to sound a little corny :P).
You do need to be careful when you do fully retract your foreskin atm while it's tight and be sure not to leave it retracted over a long period of time as it could cause 'paraphimosis'. Simply retract and leave it for a couple of minutes, then move it over the head of your penis and then repeat. Do this everyday over a period of time that suits you. Hope i've helped you out!
First see a doctor and thats a must.
Second, did we not play with ourselfs as a young boy, then its not to late, a good old jerk off under the sheets wont hurt and this will help you getting the foreshin back and forth but use oil, good old baby oil will do, and try pulling the foreshin to streach it.
Third try the old stinging nettle against the helmet, this will help get rid of some of the sensitivety, the first swish hurts but after that it will deadern the skin and away you go, give it a good dose all around the helmet and this is done with the foreskin back as far as it will go, it worked for me, you will start to get the sentsation back after about 90 minuts as it starts to tingle and any other effects will go.
But first get the streching going, and dont be affraid to jerk yourself off, remember your **** is your best friend and lover who only knows you best
Talk to a doctor. One of the arguments used in favor of leaving things natural is that it keeps the head of the penis nice and sensitive to sex ... some male writers say that a circumcised penis head gets so desensitized you could rub it with sandpaper and it wouldn't be bothered. You, on the other hand, have a penis head so sensitive that it can hardly be uncovered without hurting. I would check with the doctor to make sure you don't have any kind of infection, and to discuss the inability of the foreskin to retract comfortably. He might recommend a deadening agent like lidocaine, but of course you wouldn't want to use so much that you don't feel anything during sex. And he might have some suggestions regarding how to get the foreskin to stretch back more comfortably. Good luck!