Alorna, I'm very sorry to hear about your situation. It must be so difficult trying to figure out whether your marriage can or should be saved; and it would be much easier for you to leave him if you didn't have to worry about losing your child or even leaving him alone with your husband for visitation. I agree with the posters who have suggested that you seek professional help. Most women's shelters have counselors (and you don't have to be a victim of physical abuse to seek help from them, they help women who are being emotionally abused, too) and some are able to refer you to lawyers who do pro bono (free) work with women who need help.
My opinion, based solely on what you've written, is that your husband is addicted. Here's a very short news article about pornography addiction that may have some helpful information for you: http://tv.ksl.com/index.php?nid=5&sid=40866 (Pornography: A Serious Addiction). Several months ago, I read an article about a research study that showed that viewing pornography stimulated the same part of the brain as using cocaine.
Also, he's being controlling and extremely unkind to you. That is harmful to you, and also to your child, whether it's caused by his addiction or is in addition to his addiction.
Addictions are so difficult to deal with that many colleges and universities won't allow undergraduate students in the helping professions to provide counseling to addicts unless the student himself has overcome an addiction.
My closest experience was with an alcoholic who worked for me my first year in the AF. He was a guy who could be charming and manipulative, but he was affecting our unit because his alcoholism caused him to make mistakes and to slack off work. On the advice of my superior officers and the senior NCOs in my unit, I gave him letters of reprimand, ordered him into alcohol rehab (one advantage the military has over the civilian workplace), counseled him repeatedly. His wife left him as his alcoholism progressed. He tried to quit drinking, but nothing would work (and he also wouldn't attend AA since he insisted that he wasn't an alcoholic, that he just had a "drinking problem", and he tried to blame his "drinking problem" on everybody and everything else he could think of ).
Finally, everybody told me that I had to bust him (demote him to the lowest rank) and order him into detox (as an inpatient) and rehab. I would have done anything else if it would have helped, but the drug and rehab counselors showed me that it was the only way to get his attention, that by busting him he wouldn't have the money to buy alcohol. I don't know what ultimately happened to him since he was transferred out a few weeks after finishing rehab.
What I learned is just how strong an addiction can be and that an addict can lose everything (spouses, other family members, friends, jobs, etc.) to the addiction.
Employers, such as the military, have had to deal with drug and alcohol addictions for years, and now they're having to deal with porn addictions. Recently, two men who worked at the same base as my husband were disciplined and discharged from the military because they had been downloading and/or viewing pornography on the computers at work despite numerous warnings (not to them individually but to the entire base) about this.
Even if you're on the right track, you'll get run over if you just sit there. Will Rogers
To love at all is to be vulnerable. Love anything, and your heart will certainly be wrung and possibly be broken. C. S. Lewis