Ask him to define it. It could be length, it could be purpose or intention, it could be measured physically. It's important to find out from him, what he's asking.
You care most about each other and always omit others;Your friends know the whole story;You have some kind of lover rings,moreover, you take some wedding photos and show them to parents and relatives.
I think it would be a relationship were u think u are with the perfect guy and you love him uncondicionally and it is not just to have a boyfriend or something like that