I don't think he was ever having fantasties about it in any way other than being horrified.
Sorry my English is ok, I guess, but far from native speaker level. Fantasy is probably the wrong word. He was disgusted from the very beginning.

@Tushabuv:
What has taken me with him? We used to have these deep conversations. He is a very kind person and he really does put the relationship first. He is multitalented, a musician, a filmmaker, a nature lover.
I regret so much about my past. Not only how I went about sex. He is so much more mature. He showed me a lot of important things. Like the value of family. I wish I was more like him. I aspire to... And I was with so many men who only wanted me a little but not for real. I thought this was different. I ruined it...

We just had a fight about the threesome again. Or about the part where I had sex with a woman. He wanted me to explain. He is always expecting some kind of mature explanation that I can't provide

He said he is exhausted and miserable because of our relationship. Basically he called it off. I started to get my things. We were both crying and really upset. He says he didn't cry in years.
We ve been at this point so often. But this time was different.
He started to hug me and touch. In the end we had sex. Afterwards he said he was sorry about it.
He said he doesn't want to live anymore...
I don't know. I wish I had gone...
Sometimes he says that there would be no point in returning to someone who has a past like mine. Today he said maybe after some time we might find back together.
I guess I will have to accept. He doesn't want to break up. But it is torture to him. I can't make things better for him. I feel so sick.
And bad because I stayed.