The 12 Steps are for Those Who Are Beaten
As for me, the question is not whether you need a twelve step program, but whether you are beaten yet. If you believe that there is still hope for you to quit by your own willpower (with occasional chizzuk, of course), then I see no reason to quit trying. I kept trying for years and years and never gave up until I saw that I had really lost, and would only get progressively worse till I lost everything. I saw that I was coming down the pike for some time already but never really did anything about it (beyond the same old silly "trying harder method") until I was forced to.
If this question really bothers you, I would suggest you do what I did and write out your entire lust-use history. From the very first time you recall doing something with lust that you regret or got into some trouble, and continue each behavior till this very day. After you are done, look at the entire pamphlet - better yet (as I did) read it to a trusted person (who will not vomit). Then I believe you will be able to answer your own question.
The only other answer I personally know of, is to go ahead and try to work the 12 steps with a sponsor in a fellowship (like SA, for example) and find out if it is right for you. 5-6 meetings ought to do it. That's a rather tall order for the uncommitted, but some do it. I do not pretend to know whether anyone needs to go to SA and I would never pasken that anyone is an addict, besides myself. These are decisions that my heart tells me an individual must arrive at for themselves. As Rabi Elazar ben Durdaya said: Ein hadavar tolui ella bi. If you do need it, no one can ever surrender to the facts for you, anyway.