I have no idea what this could be but it flares up periodically. It doesn't hurt but stings very slightly if I get urine on the tip of my foreskin. Usually clears up in two weeks or so but i don't know what sets it off in the first place.
Chy, how long has this been like that? I am wondering whether you can expose the head / glans of your penis - or whether you have tried at sometime to force your foreskin to reveal the head / glans of your penis?
The swelling you have certainly is not normal. The conditions you potentially have are Posthitis or Balanoposthitis - when you say that you are not sure what sets this off it could be an irritant of some kind that is causing this.
I wonder whether you are sexually active? Some sexual infections can be the cause of conditions like this. It would be best if you get this medically checked out: can you get to see a medical professional such as a Doctor, practice nurse or go to a Sexual Health Center?
Until you have had this checked you need to use water only to clean your penis with and you must make sure the area is kept dry, so either carefully pat it dry with a clean towel that only you use, or use paper tissues or toilet paper to carefully dry the area after you have urinated.
You need to get this checked and the right treatment put in place as soon as possible as this could develop into a very serious condition …