The penis basically consists of 3 balloons that fill with blood on erection. See Diagram: http://en.academic.ru/dic.nsf/enwiki/265769o
This page shows functions and mobility: http://www.circumstitions.com/completeman/
Masturbating can be damaging to the penis if you apply too much pressure. It damages the spongy tissue chambers of the penis. Consequently the 3 spongy chambers do not fill out with blood and expand the skin. Normal healthy penises will get spontaneous erections, especially at night and in the morning. If you damage the structure of the penis, this does not happen. Spontaneous erections help with the stretching of the foreskin.
The collapsed inside structure of the penis, as well as the lack of strong, hard and long-lasting spontaneous erections leads to a tight foreskin because on erection there is no strong pressure pushing out against the foreskin. P.S. A sensitive glans (head) is a sign of damage. Many people complain of this on the network54 forum
So what you need to do is allow repair of the 3 spongy chambers to happen. Don't masturbate as much. I would aim for once every 4 days at the most. Take cold showers to reduce the hotness and horniness.
When you do masturbate, don't do it for a long time. Your body will repair what needs to be repaired. It can't repair if it is in use.
Another thing. Too much masturbation (especially with the wrong technique) can cause micro-tears in the skin, which form scar tissue; scar tissue is less elastic than unscarred tissue.
So, when you masturbate, make sure you are not applying too much pressure or using a damaging technique. Don't push down on it through clothes, or hump the bed with your body weight on the penis etc. Just lightly grip the penis and move the foreskin up and down. The penis was not meant to have large pressure applied in a death grip. The vaginal walls are soft and the action of intercourse is merely to move the foreskin up and down.
Once the inside structure starts to repair, the 3 spongy chambers of the penis will inflate to their proper position. This in itself will expand the foreskin over time even without erections. With frequent spontaneous erections obviously there will be more pressure pushing out against the foreskin.
You should be getting spontaneous erections. This is a sign your penis is repaired. Ideally you should aim for prolonged strong erections. Morning wood is an example of this. If you wake up in the morning and have an erection for an hour - this is great. These prolonged strong erections will maximise the expansion and stretching of the foreskin.
Because the sponginess of the chambers is restored, there will also be extra 'give' when trying to pull the foreskin down. To understand what I mean by this, imagine pulling a jumper sleeve with a small hole over a long balloon. The balloon doesn't fit through the hole at first, but if you pull hard, the balloon comes through the hole because the balloon compresses and gets narrower. By restoring the sponginess of the penis you make it easier to pull the foreskin down. See diagram to left.
As a test for how much the spongy chambers have repaired, you should be able to move your erect penis up and down without touching it just by contracting your kegal muscles.
If you have damaged the spongy chambers then it will take about a week-2 weeks for good repair progress of the penis. Once the penis is repaired, it will take a few more weeks for your foreskin to become looser. If you follow my advice exactly - exercise, nutrition (see below), I would take a conservative guess than it would take 3 months at the quickest. If you want to add in the conventional advice of stretching - ok - but the natural stretching that a strong erection gives in my opinion is best.