Suzy,
I think marriage counseling is not a good idea in your case. I understand others who suggested it, but in my experience marriage counseling is only useful when the two spouses misunderstand or miscommunicate, but respect each other in general. If there is a major issue with one partner, then that issue must be addressed first.
In the case of abuse the abuse must be treated first before marriage counseling will have any benefit.
In your case the online porn/dating is emotional abuse and your husband has a serious problem. If he restricts it to fantasy flings and not meet anyone physically, then that might be his excuse to not feel it is wrong. It is wrong, as the feelings he is looking for are as real in an online fantasy as they are in real physical life.
It is not physical adultery, but it is 100% emotional adultery. It is 100% emotional adultery, even if the person on the other side of the online relationship, whom he believes to be a young beautiful porn model, is in fact a disgusting, obscenely ugly, dirty, geriatric homosexual.
If your husband does not want to change or does not see anything wrong in his behavior, then divorce seems to be the option.
About love. Love is a complex combination of many fluctuating emotions. I was wondering if the love you feel is towards the man you thought he was, before he showed another side of himself. Many women who have been abused say "But I loved him." What they mean is that they were in love with the persona they fell in love with, and cannot grasp in their hearts that the real person is someone else.
If there is a possibility that he will change then there is hope, but if he is going to continue behaving this way, then I'm sad to say I agree with the advice by kim12345 in post #5.
[h=5][/h]