My boyfriend acted out online, exchanging email and phone calls with someone he met in a chat room. He used a public computer and his cell phone. This meant that he was out of the house sometimes and I didn't know why-- 45 minute trips to buy milk, having to leave early for work, etc. When I would ask him about these absences and his general withdrawal from our relationship, he'd act very flustered and hurt, accuse me of not trusting him, not understanding him... basically he'd leave me stuck in a situation where I didn't really know what was going on, but I didn't think it was all okay either, but the only way I could make him feel trusted and not betrayed was to drop it.
He ended this online thing way before I ever found out about it, and he carried around a lot of additional guilt and fear about me finding out. When I asked him why he never felt like he should stop for my sake, or why he didn't tell me after he'd stopped it, he said, because I didn't seem to care about it while it was happening. According to him, he was clearly giving me bullshit answers and excuses and the fact that I was accepting them meant that I didn't really care about the truth of his situation, I was just like all the others who only saw and heard what they wanted and didn't bother to look for anything else.
That really, really, pissed me off. I had asked him for answers over and over. I worried about it all the time, and he brushed it off or accused ME of betraying HIS trust. When I'd asked him if everything was okay with us and he'd "Yes"-ed me to death and then gotten all pissy and stormed out the door, what did he really expect me to do? Follow him? Read his mind and know that he was re-enacting some angry>