What should I do? Need urgent advice about this. Help please!?

I've been with my boyfriend for 3 and a half years now. We have had some ups and downs like most couples but although ,it sounds cheesy he is 99% perfect and treats me like a queen.I know that in many respects I am lucky to have him. However the other 1% is the real worry for me. A while ago and after much suspicion on my behalf, we had a very deep discussion in which reluctantly confessed to me that he is " addicted to internet ." I was very upset about this and went through all the natural emotions and feelings about what I felt must be my own ual inadequecies and it took me a while to recover my self esteem. He swore he wouldn't ever do it again and has stressed repeatedly that with me is absolutely wonderful (HUH?) He says that he "can't stop doing it as its something that he's done for years and its now habitual" However to cut a very long story short.. despite my forgiveness and attempts to understand this behaviour and his promises that he would " never do this again" I was devastated last night to find out he is still doing it. He says " he doesn't like doing it (WTF?) but of course he must do or he wouldnt be going back there when he knows the absolute devastation it causes me emotionally. To add to that further after the last time (he's done it at least 6 times now) I gave him an ultimatum.."it either stops or I am out of here!" . He knew that I was serious about last time and I feel that he's definately put this obsession above me and my feelings and disrespected me totally in the process. I've now told that I can't go on this way and he is devastasted. He has swore he will seek help with this and actually went to see his GP this morning about a referral to a specialist. He wants me to accept this and move on. However I really don't know that I can wait about for this help as I still don't know if there is anything that can be done about it and I will have wasted far too much time being really upset about what he is doing. I feel I need to move away from this sordid little part of my life. I love him but surely there's only so much anyone can take. Please don't say " its not cheating" . Looking at and lusting after other women, even if you aren't actually sleeping with them is betrayal. Despite what he says to me about our life being wonderful, I feel it can't be as if it was he would not need to do this. I love him but really think he has overstepped the boundaries of respect now. What do you think?