I have to say, I think it's a bit of a leap to assume because a man masturbates frequently he has an addiction to porn. My H has a very high sex drive and even tho our sex life is very much back on track now (as some of you know we're still in the begining stages of this), he has always been open with me about masturbating almost daily. Even now that we are having sex frequently he masturbates. He has such a high sex drive that I don't think I could physically keep up and he doesn't expect me to. If he needs more I would much rather he look at pics on the computer and take care of business himself than go find someone else to fill the "gap"!
Having said that, and not knowing all the background, you mentioned that you never say no to him. How often do you initiate? How often are you actually having sex? It sounds from your post that the masturbating has taken the place of sex with you, even tho you're willing. Now that's a problem. But perhaps he needs you to initiate to feel you really want and need him?
I'm not sure I agree with interrupting him and trying to join in...he might be embarassed at having been "caught", and the situation may not turn out how you would like. Even tho it's bull, most of us had it instilled that mbing was wrong and if you were doing it you should be ashamed. I think talking to him during a relaxed time in a non confrontational manner may be better. I think the first step to knowing what YOU need to do to address the problem is understanding what the problem is... understanding where he's coming from and what his thoughts are. The only person you can get this information from is him.
I know from my own situation that had open communication happened sooner, where BOTH people were communicating honestly, alot of heartache could have been avoided. Good luck to you...
Me:40 (LD) H:46 (HD) T:9 M:4 1st bomb:H PA in 2002 (before M, but living together. It ended when I found out and we worked on things) 2nd bomb:ILYBNILWY, can't go on this way, 11-11-07 No kids together