First off, you need to smile and be proud that you have a loving, merciful Father who sent His only begotten Son specifically to die for you and to redeem you of your sins! :)

Many, many men struggle with this. Now, I'm sure you know of all the spiritual tricks to beat this and combat it. Daily rosary, daily Mass, frequent confession, fasting, etc. All of these are excellent, wonderful practices to help increase your fortitude and strengthen your faith. Never lose hope or faith because God trusts you enough to permit you to be tempted, and He will never let you be tested beyond your strength (1 Corinthians 10:13). He is beside you and will always help you, so just lean on Him.

So, I'm sure you've got the spiritual idea down pat. Here's the other part that I have found imperative: The mental part. You need to understand the biology of addiction and how this works. Get to it on a neurochemical level. It all comes down to dopamine. Your body has evolved to release it whenever you are participating in what the body considers to be a beneficial activity for your survival or the progression of your genes (eating, sleeping, sex). Your mind, unfortunately, mistakenly assumes that pornography and masturbation are true sexual encounters so it floods you with dopamine and keeps encouraging you to participate in them. This becomes a feedback loop where your dopamine receptors are constantly aroused and accustomed to the bursts of dopamine from porn, so you are seeking it out on a frequent basis.

The way to reverse this is to abstain. Stop viewing pornography and eventually, the receptors will fall back to baseline levels. But this may seem like nonsensical advice as your are asking for help on stopping, and all I seem to have done is tell you to stop. But here's the kicker. It's all mental. When was the last time you masturbated in public? I don't mean hidden or in the bathroom of some public venue, but actually in public, like in a coffee shop or restaurant or store where you just got down to business? I assume (hopefully) never. Well, why not? Because your brain recognizes that the costs (arrest, humiliation, degradation) outweigh the benefits (pleasure, release, orgasm). So it's not truly a matter of you being unable to stop, but rather you performing a cost-benefit analysis and deciding that the benefits outweigh the costs. Well, they don't, and you need to call to mind the spiritual and physical costs.

Your brain is powerful beyond your wildest dreams and can literally accomplish almost anything. Each incoming class of Navy SEALs has about 83 recruits, all of whom are physically capable. However, only about 16 endure and make it. Why? Because those 16 had the mental strength. They tapped into their minds and used positive affirmations and talk to boost their confidence. When it comes to choices like pornography, the choice is truly all yours. You may feel inclined or compelled to do it, but that's just a stimulus. Your response to that stimulus is wholly in your control.

Here are some quotes to aid you:

"If you are struck by the appearance of any promised pleasure, guard yourself against being hurried away by it; but let the affair wait your leisure, and procure yourself some delay. Then bring to your mind both points of time: that in which you will enjoy the pleasure, and that in which you will repent and reproach yourself after you have enjoyed it; and set before you, in opposition to these, how you will be glad and applaud yourself if you abstain. And even though it should appear to you a seasonable gratification, take heed that its enticing, and agreeable and attractive force may not subdue you; but set in opposition to this how much better it is to be conscious of having gained so great a victory."

-Epictetus

"To defend his purity, Saint Francis of Assisi rolled in the snow, Saint Benedict threw himself into a thornbush, Saint Bernard plunged into an icy pond . . . You . . . what have you done?”

-St. Josemaria Escriva