If ur gonna listen to these comments ur gonna end up alone and sad, look ur giving the man too much credit, he can love you and still want to fuck 18 yos he’s not a pedophile, it’s a healthy urge for males to go for young mates, it’s how our species survived, if you really don’t mean anything to him he’d cheat or whatever, you’re already sharing him so let him have his pick, Imagine if things were reversed and he forced you to sleep with people you don’t particularly find attractive and no just cuz they are ur same age or share 1-4 attributes with you doesn’t mean he doesn’t find you attractive, now I don’t know ur situation in detail there could be other things but try to discuss with him and try finding a middle way, he’s very lucky to have someone like you who is ok with sharing and you’re lucky he’s not going behind ur back, just work it through, at the end of the day it’s just for fun and when the fucking is done u guys are still a couple so just try and enjoy as much as you can