My dp has loads of friends from uni who, due to the nature of their shared profession, are all over the world. Because he is more of a girl's guy, I'd say 70% of them are female. He chats to at least three friends each day via messenger, perhaps sending a funny meme that they'd like, or asking about an event that he knows is coming up for someone, etc. I'd say two of them are female on any given day.
It's not a big deal to me at all. They're his friends.
However if he started constantly talking about his relationship with me, with particular friends, female or not.. that would be a bit strange. I'd wonder why he wasn't just talking to me about our relationship!
My DP mentions me to his friends, he certainly talks about what we've been up to and so on. But full on deep relationship chats, on a daily basis? It's slightly odd. I don't even think I do that with my own female friends. It would bore them to death.
Your bf is only 25, that's young, particularly for a man, and particularly for a man who has a "sensitive side" (i.e. who doesn't fit the mould of the average lad who just does what all other lads do, in a socially acceptable order). I'd assume that he is still testing out scenarios of what his life might look like... with you, with other girls, in another town, etc. etc. He can love you as much as he likes, and want to marry you, but that doesn't mean he's actually ready to do that.
It's really unlikely this relationship will last. The foundation doesn't sound strong. He has a lot of growing up to do, and that's ok, but don't let him try to convince you that he totally has his head screwed on, this is all fine, etc. Perhaps lower your expectations and start looking around to see if you won't be happier and feel a little better if you moved on. It's not meant to feel this way - good relationships are meant to feel solid and secure x