I don't know what, to your H, would constitute being "sorry" but I know, based on your description that what you are doing and saying isn't it. I think your H may not even know what it is that you could do that would look "sorry" enough. I would be tempted to ask your H if you stopped going out, quit work, stayed home all the time, slept on a bed of nails, washed his feet every day while chanting "I'm sorry", if that would be enough... I would bet it wouldn't. It wouldn't simply because he can't wrap his mind around being able to forgive you. He can't do that because he hasn't recognized his contributions to the problem. You can't do that for him. He either gets there or he doesn't. He either decides to love and forgive or he doesn't.
I don't belittle the pain and humiliation your H must feel. However, only he can get past it. So far, he just doesn't seem to want to. He wants to marinate in his pain and for you to do so too. Recently, I asked if you were done. I asked because you sound done. If you put a date on things as Corri suggested I wouldn't make it too far down the road and I wouldn't keep it to myself.
What about this conversation? "H, I cannot continue living like this. I have apologized. I have repented. I have been punished for the last two years. In the next year, if I don't see some signs of healing then I will know that this marriage cannot be fixed. I am sorry for what I have done and I have great hope that we can find our way back from this. Hopefully, to a relationship that is better and more fulfilling than before. However, if we can't then I am ready to live separately and co-parent our children from separate residences. I would know that this marriage was healing if....(put your own description here)"
See Heather, it is not having these kinds of necessary conversations that resulted in making an affair so attractive. You cannot continue having conversations that are "You ask a question or voice a concern. He blames or deflects. You walk away and do whatever you think is right." I'll bet the current pattern is part of what things were like before the affair, part of what made another person attractive. I'll bet the other man offered an openess and an acceptance that you didn't have with your H. The current situation is probably what was going on between you before the affair just amped up and verbalized, with your H feeling that he now has the moral high ground to do and say whatever.
I am not telling you to end your marriage. I am not saying that your H is a bad guy. He is a hurt guy. He was probably hurt by someone long before you two ever met -parents? peers? girls? He is protecting himself from you and anyone else who has ever hurt him in the past. You can offer him compassion but it is he who must step out of his comfort zone. I hope he does.