My (25f) boyfriend (25m) said he thinks about sex with other people. I’m not sure where this can go from here?

Sooo… we have been together since we were 15. We have never been with anyone else sexually. I was broaching the question of why we are not yet engaged or if/when that may happen and he eventually told me he thinks about what it would be like to have sex with other people and more generally he is unsure if he is ready to commit to this to relationship.

I know we are young so I don’t know whether it’s stupid to expect someone of our age to want to be somewhat committed or feel it’s heading that way. So part of me is happy to just continue as we are.

I don’t want sex with other people because I don’t have as much of an interest in sex. He says our sex life is good and there’s nothing about it he would change so I’m just confused.

Since this conversation he has been a lot more “romantic” and really wants to try and make things work out for the best and I appreciate the effort.

I just can’t shake off the feeling that I’m not “good enough” sexually or generally for him. Or whether this can be worked through and I can eventually get over it as other threads suggest that lots of people think about this (I’m guessing more likely if you haven’t had loads of sexual partners) so I feel like I’ll always be in this situation no matter who I’m with.