Hi Barbara, I'll tell you why I held back on giving details.
There were several reasons I said I didn't remember the events of my affair. One was embarrassment. I was ashamed to tell my husband some of the feelings I had and some of the things I did. It painted me in a very bad light. Yes, the affair itself did that, but I knew the specific details would make it even worse.
Another reason is that I knew the details would be hurtful to my husband. I'd already stuck the knife in, but telling him some of the sexual details or things the OM and I did seemed like I was just twisting that knife in even further. There was also the fear he'd leave me if I gave him all the details.
At the time I ended my affair and told my husband about it, I remembered pretty much every detail of what had gone on. At that point saying I didn't know or that I didn't remember was a lie. Several years later when I finally did start talking about my affair there were details I simply couldn't remember, and that was the truth.
We're almost 7 years out from Dday. I can remember events, conversations, and pretty much the timeline regarding the beginning and ending of the affair. But there are some details I really can't recall.
I didn't think my husband was stupid. I believe it was more of a.......what he doesn't know won't hurt him. I honestly believed that it was better to keep some of the details from him for his own sake. It wasn't until years later that I realized I hindered our healing process more by withholding details than had I told him the full truth upfront. I can tell you that as WS you just don't get how important that is until you find a site like this one. I now realize it wasn't my place to decide what was best for him and what was not.
>>So, what is my H's problem?>>
There are probably several reasons he's holding back. He thinks he's protecting you. He may think you'll leave if you know all the details. He's embarrassed for what he did. He doesn't realize how important it is to you that you have all those details.
>>I swear I will give up if I don't get answers>>
Barbara, one thing I remember is how my husband reacted when I did give him answers. I usually gaged how much I told him based on how he reacted to the previous question. Talking to him about my affair and sharing details was like sitting and rubbing salt on someone's open wound. You see the pained expressions on their face and you see them trying to hold their composure while you're heaping hurt on top of hurt. If you feel any remorse at all for what you've done it's tough to keep that conversation going. And to keep firing darts at them.
I hope this helps. 
GT