<human>: Hello,
My SO and I were on holidays the other day (which was amazing). It was our last night and we had a long drive back. We have been together for about a year. Things have been amazing so far, everything about him and our relationships is what I have wanted and is everything I need. 
We got to talking, I asked him something I had been dying to ask him for a while. Where do you see this going? I know in my heart that I want to marry this man, he is the best thing in my life and I have no idea what I would do without him. He said he wasn't sure. Fair enough it has only been a year. He said that everything in our relationship is absolutely perfect except one thing. Uh Oh here we go. He said he feels trapped by our sex life (we have a great sex life he seems happy and its always fun). He said he meant that it's an amazing sex life except he wonders about sex with other people and the whole sleeping with one person for the rest of his life and if he is ok with that. I started crying my eyes out. I didn't know what to say to him so I retaliated saying well I think about that but I just don't tell you about it. I didn't mean that I never think about anyone else but him in my life. Now I feel even more horrible.
He always talks about how we have so much time to do amazing things together and how much he loves me. He is always suggesting we live overseas together and travel the world together. Just this was devastating in an otherwise fantastic relationship.
I want to tell him how much he has hurt me by saying this. I just don't know how to approach this. He is finishing at work in a few days to pursue something new and I am about to go into uni exams. I just don't want this eating at me.
I can't stop crying about this.

Can you succinctly summarize the text in 1-3 sentences?
<bot>: SO said everything about the relationships is perfect but feels trapped by our sex life and wonders about being with one person for the rest of his life. How do I approach this.