I voted maybe becuse, (much like Oldsoul stated), this involves two different people with two seperate opinions.

It is my opinion that if a relationship is mutually failing, with both aware of this, without either attempting to correct its demise, then online contact, (for whatever they offer), is not considered cheating. After all, what is there TO cheat on?

However, in your situation, with your relationship going through the "happily married" scenerio, and your partner is seeking gratification elsewhere while allowing you to believe that "all's good", then, I'd have to say that, yes, in this case, it is considered cheating.

He had willfully mislead you. Since you've confronted him, he had intently made effort of covering his tracks..locking you out. THAT is a direct indication that he very well has something to hide, (if not regarding this woman whom you discovered, then possibly of another), regardless, he has violated your trust, and this should not be your burdon to correct.

I feel, however, that seeking more evidence of his betrayal is not healthy behavior for you to proceed with. This will only deliver you further misery. It already is. It has consumed you. It is transforming you into someone you clearly are not, which only adds to your inner misery, not to mention that it is constructing much harbored resentment toward your hub due to the fact that it is because of him that you are behaving like this. This is NOT what you want. This harbored resentment is only adding salt to the wound, compounding what is already traumatic for you....digging this hole deeper...and possibly creating a sense of hopelessness for you.
With harbored resentment only comes anger and, if allowed long enough to fester, hate. You want to avoid this at all costs. Distrust is more than enough for you to have to deal with at this time.

The healthy possible soltution is for you to confront hub with joint counseling.
Obviously, you have made him aware of where you are emotionally regarding all of this. You are still uncertain of 'exactly' where he is emotionally, and apparently he is reluctant to provide you with that.
From your description of your marriage, it is WELL worth the effort of seeking counseling and strive for a mutual solution to this. He must be willing, however. If he is not, I suggest then, that you seek counseling for your own self to overcome this new obsession of seeking his further betrayal. You are in need of support. You deserve that, if not by him, then elsewhere. Do not allow what he has done to you transform you into someone you don't even like, yourself.

From what you have said about his little trip, it is my understanding that I don't think he followed through with the meeting. He called you every half n full hour while away. Returned the next day. You read in his follow-up email that it didn't happen. Then, accept that for what it tells you. Although, I understand that because of his betrayal, it's difficult to have faith in that...but, try to read that for what it really says. Personally, I don't think he did meet her....and THAT alone really does make a statement. I think he couldn't go through with it. THAT just may tell you something..wouldn't you think?

I'm an optimist. I try to see the good in any situation, however, the fact that he continues to lock you out of his systems is an indication of something not quite right. And that so needs to be addressed. He has NO reason not to trust you. Perhaps, his actions are signals of guilt...regardless...that is behavior that has no place.

Counseling is about the only hopeful solution to this matter, from what I can tell.

I am so sorry that this is happening. I understand your pain. Been there myself, (with the inclusion of hub's serious addiction to extensive porn for many years).
The best you can do is to do what's best for you. Once you've got yourself stabilized, then you can approach this with confidence?

Best wishes and many, many ~

Shangrala