he doesn’t think it’s appropriate for me to go and stay with her overnight like I used to, for example
Yes! No wonder!
Can you really not see why he's be pissed off or uncomfortable with that?
He's starting to realise that a bit of fooling around isn't as casual as what he once thought, that you are in fact bisexual and you're expecting to stay overnight with someone you were once sexually involved with....and you expect him to be ok with that??
I don't often point out double-standard on Mumsnet, but this is one where I can see that there is.
To those who think he's being controlling - when you agree to be in a relationship, it's not like being friends with someone, ffs. This isn't school.
You enter into (usually) a monogamous situation, a sexual pairing whereby it's not acceptable to push someone else's boundaries like this. People will say 'Well he should trust you'. Yes, but it's not one-sided, is it? One must learn when it's appropriate to give, but ALSO when it's not appropriate to take or expect things from others.
I understand that you may be more suited to different, more relaxed type of relationship, but he's also not wrong for being unhappy with all of this.