You should want to stop to be able to have a life, NOT to stop 'sinning'.
If you don't stop now, you will end up spending your whole day online looking at P***. You will have no life. You will not learn Torah. You will ignore your wife and kids. You will not get a position, nor be able to hold down a job.
So how do you stop?
Well that's what this site is for. I was crazy till I found this site. Then I learned to stop trying to "stop" and start living instead!
Let me explain.
Step 1: Admit you have a problem that you can't control. Post that here on the forum, post it often, and don't forget it.
Step 2: Don't resist the urges, cuz that just makes them stronger. Instead, gently put your mind some place else.
If that does not work, tell yourself "I will wait 15 minutes and then I will allow myself to do whatever I want". During that time, do something you enjoy. That might help you. If it does not, you will at least have the merit of those 15 minutes. Keep building your merit, and ultimately you will succeed!
And one last BIG SECRET: Post here on the forum often and tell us about your struggles and victories!