Speak to him about it.
We can't give you advice on this because we're only hearing your side of the story - and unless you ask him, that's all you're hearing too. Maybe he thinks your relationship is at some sort of level where you don't constantly have to be around each other to know you're wanted; maybe he genuinely has lost interest. Maybe he just wants a bit more time to himself - of course he meets up with other girls more, because they're plural. He might meet up with each individual one less than he sees you, or he might only see them in large groups but he sees you on your own, or something.
It's all hypothesis - ask him, that's the only way you'll know.