Hi guys here's my story,
I am struggling with lustful thoughts about women I see. I work in a secular environment. I am well liked and respected. I am happily married with wonderful kinderlach. sometimes I find it impossible not to start to masturbate at night when I am alone.  I try to stop my impulse, , this happens maybe 3 times a month, feel very shamed the next day, even if I don't go to zava.  I want to eliminate this behavior altogether.
appreciate any feedback.

Welcome

I feel for you - I was there
(almost last night too)

Welcome 

recovery should be with Hatzlacha

Been there too. We'll definitely not starting in the first place is a good idea- but how can you help yourself not do that? What are YOUR thoughts? Have you tried any way of stopping? 

Welcome!  Did your story start when you started working, or does it go back further?  Do the women at work act in a provocotive way towards you at work because you are respeced?  Please share more about your struggles. I have a hunch that you have much more to share. 

Also, please check out the handbook. It's a good place to start.

Welcome Chaim.

What triggers your thoughts?

Is it sexual lust, or a feeling of loneliness?

Are you stressed?

I appreciate the feedback. I started masturbating as an adolescent and it became an outlet to relieve anxiety and loneliness.  recently I have been listening to shiurim by Dr. Dovid Lieberman. He emphasizes the ego's desire to take us out of reality. Fantasizing is nothing less than that. So I am looking into that angle.  He also speaks of cognitive dissonance, which as I understand it is behaving in a way contrary to your desired core beliefs.
I like the concept of making a short term shuvua with consequences based upon whether I fulfill the minimal requirements to stop behavior with a small penalty vs a large one if I don't.  I am quite sure that my position of authority at work plays into how woman interact with me.  It is a very interesting interface between a frum man trying to be true to his beliefs and the general mode of behavior in the secular world between men and women. It was actually my desire to work on guarding my eyes that brought me here. 
I find that saying tehillim helps me to calm down.

Gibbor 120 mentioned the handbook. where is that

guardyoureyes.com/the-gye-program/free-handbook

(top of the page under GYE Program)

Do you still suffer from anxiety and lonliness?  If so, dealing with those issues will help a lot!