I am a regular poster and NCd for it as it's mortifying for me.
Me and DH have had a great sex life even after having our DCs. It never lacked in any aspect or imagination and we were both quite happy with it. Over the years we have started to experiment slowly. Again, we have talked about everything beforehand and everything has been consensual from both sides and thoroughly enjoyed.
some months ago, DH shared with me a fantasy that he says he has been having since ages but hasn't been able to tell me before. It's him seeing me having mind blowing sex with some random hot blokes (more than one even!) that HE brings home. I suspect he is actually refusing to elaborate this as there is more to it, like may be it could be people we know? But I don't know as he got evasive and didn't explain further. And he wants me to do this for him too. That is, bringing hot girls for him or even couples.
He refused to elaborate further as I think I looked too shocked already.
I have been trying to find ways to talk about it but he has always laughed me off saying it's just a fantasy he has and he never wants to act on it. A couple of times he got very defensive and said it's something every man secretly thinks of and never acts on! 
It has been months and it is now a regular part of our intimate time together and he says he is very happy about the things that way and that it. I wouldn't lie. After the intitial shock, I found it very flattering and arousing that he is fantasising this. It took us to new heights. But it has worried me too.
Is he thinking about other women and trying to find a way around that by offering me to do it too? Or is it a genuine real fantasy that men haave secretly and he is telling me the truth? Am I overthinking it? I would probably never be able to act on it. He is the one for me and always will be. It's just the fantasy part that is arousing for me. So may be it works the same way for him and he isn't actually thinking of anything beyond this?
He has never given me any cause to suspect him and we were really good friends for a very long time before we started dating so I kind of know his history and personality IYSWIM?
I hope I could get some answers here as he has said he has told me all that he thinks there is to it.
Thank you to everyone who has read this very long post. I really do need your advice and experiences please.