My husband is addicted to adult movies, recently i've noticed that he's been a bit more active with himself and less so with us as a couple

My husband and I have been together for 8 years, married for 1, have 2 kids (5 and 10) and are in our early 30's. We have a healthy sex life, I like to be regularly sexually active and creative, as does he and i've always been fully aware that he enjoys porn, sometimes cam sites and i've never had a problem with this as i believe it is not a reflection of us as a couple and is something most men happily experience on a fairly regular basis. 

However recently i've noticed that he's been a bit more active with himself and less so with us as a couple which is fine by me as he's been working a LOT more recently and i know he's very tired so Im sure he's happy to just relieve a little stress. The problem for me though is that i've noticed he's masturbating at EVERY opportunity and this worries me. He came inside from fixing the car to 'sort himself out' while i nipped out to pick the kids up from school which takes 15 mins, the following day he went upstairs to our room while i popped out to pick up a take away and the kids were in the house at the time which really bothers me! Those are just a couple of examples but you get the idea.... 

We have a good relationship, we talk a lot and laugh a lot, we're generally very honest and open but i feel like i would embarress him by calling him out on the issue and he would probably become angered by it. I guess what i want to know is, does he have a porn addiction, could it lead to something worse, like an affair? Is there something i should be doing or saying, i'm quite confused by it all or is what he's doing normal? 

I've asked this question on another site and was spammed with rude and unhelpful messages so please be kind :)