My boyfriend wanted to sniff my daughter knickers & I let him?

To cut a long story very very short. I met this guy online in August whom I stated dating. Even though I found him interesting, even from day one there was just something about him that made me wary. Interestingly enough, he was a psychologist specializing in ual Addiction. ually, he opened up a whole new world for me, yet from the way he spoke and behaved, I just had the feeling that he actually hated/loathed women. Even though we only dated one another for about 10 weeks, I called it off 3 times. There was something that made me uneasy, yet at the same time he was so fascinating. I admit, if it wasn't for the amazing , I doubt if I would have gone back. But I did. The final straw for me, and this is what I am struggling with most, is that during our time together, his desire for sniffing my knickers went to sniffing plain white cotton ones and eventually he desired to sniff my young daughters dirty knickers. Now, if I heard this from somebody me immediate thoughts about the Mother would be, how disgusting. What kind of a women would do this? When I allowed this to happen, it felt like an "out-of-body-experience", I knew if was wrong, forbidden but I could see how much it turned him on, and that in turn, me. Yet each time, after wards I would feel disgusted with myself and so would he. And he would vow never to ask again. Yet, it happened a few more times. The fact that I allowed this, scared the hell out of me PLUS the fact that he wanted this scared me. I finally ended it when his request was to get the knickers directly from my sleeping daughter. That was three months ago. I am plagued with guilt over my role in this. Why did I allow this to happen? What kind of a person would do that? Yet, there was something about him, that almost made me want to "do" anything to please him. At the ripe old age of 42 I thought I was sorted, yet he brought out ALL my insecurities and made me needy. I can't stop feeling guilty and ashamed and even worse I can't get him out of my head. It is driving me mad. I knew/know he was bad news. With his insight into human behaviour, I get the feeling he knew how to "play" me but even more scary is that somebody in his position wanted something like this? What does that mean? Now I know, I cant get into his mind and it's not my job to, the question is why did I allow this to happen? Why, even though he scares me, am I still intrigued by him? Please don't judge me to harshly for allowing this to happen. Any constructive advice would be welcome.