Warning- this is not graphic but frank
Oh Katrina, this has been my life for 7 years now... I have been in your shoes, continue to be there and please know whatever you are fearing is happening- it is. You have been given lets say a 6th sense and if you are seeing the signs then it is absolutly happening.
Here is my advise from someone who knows what you are going through, and you may take it or leave it.
1. Get that computer out of the spare room, if you have to have two computers on one desk and share then do it. His addiction thrives in secret and that is too much temptation for anyone. (Imagine if you were addicted to chocolate and someone left you at See's Candy overnight with no way of checking on what you ate or not)
2. This addiction gets worse, what he is playing with and doing now will happen later... its not a "what if" its a "when" I know it is hard to imagine, I am married to a wonderful, loving, sweet guy... but all those things that he said he would never do... yeah never was just a matter of years.
3. None of this has anything to do with sex. That is hard to believe but an addiction to sex and pornography is not about the sex- its about escape and coping... this is his coping method and its unhealthy and he needs real help to find better ways to cope. So it doesn't matter if you are Pamala Anderson, it doesn't matter if you have sex 3x a day. He would still seek out this way of dealing with things until he has found a way to break the addiction and move onto real recovery. That takes help there are a lot of online things available, one of the best for you and him is http://www.recoverynation.com/
4. We have been in and out of counseling for 5 years now, we are finally seeing results with someone at LDS family services and our ward is helping to cover a lot of the cost. If you are not LDS but have a pastor or religious leader that you could talk to it helps to have them on board and many times there are funds available to help a troubled marriage. Talk to them about it. Also find a 12 step group- there are LDS ones but any of them are fanstastic and specific to his addiction they even have family support ones just for you. Becasue you are harmed just as much if not more from all of this.
5. I am the queen of non-confrontational conversations, I would rather swallow nails than confront what I think is a slip or a relapse, but if you guys are going to be ok- you have to learn to really really really talk to each other and that means even about the stuff you are scared of. If I knew the journey was going to be this bad I might of left when we were childless or even just had one. But I have chosen to stay so far and its not about the kids. Whether you stay or leave please don't do it for the kids, this has to be about you... are you happy? Can you handle what it is going to take to get your relationship to a healthy place? Do you want to be married to this man? The kids are going to suffer more if you stay and hate each other than if you seperate and are happy and healthy. You are teaching your son how to treat women, how to have a family, how to love someone, but we teach them our disfuction too. Do not stay for your son's sake, stay for yours or leave for yours...
6. this addiction is one of the hardest to overcome because the substance is in their heads, its accessable 24/7 and secret and has no outward sign of use. Your husbands recovery is his own, you need to have a recovery of your own, a set of boundaries that protect you- I am really not good at this... but they are a safty net around you so that you can stay with an addict but not get caught up in his junk. If you do not have any, I would start there if you decide to stay. Things like requiring him to be open and honest about slip ups and relapses so that you can "trust" him and not have to play detective.
This is such a hard challenge I am so so so sorry you have to go through this. Please email me if you have any questions, need a shoulder to cry on, or just want to vent. I am in UT, not sure where you are but there are some great resources available to you and I would be happy to give you more information on that.
Again I am so sorry. Good luck, please know his addiction has nothing to do with you.
Warmest wishes and a big hug!
H.