Boyfriend and Snapchat?

I think somethings going on with my boyfriend and Snapchat. Not that long ago I went on his phone and saw he had been snapchatting two girls which he said were his friends, that he's allowed to communicate with them, and it was nothing bad. Since then his phones going in for repair and he's got a replacement and he was adamant he wanted Snapchat on it. Now he's got it back his snaochatt score has just been increasing meaning he's sending and receiving them.

I just think why did he need it so bad? Why did he want it on the replacement phone so bad? He won't talk to me over Facebook etc when we're not together but this score just keeps increasing. Its like he's talking to someone else instead of me.

If I ask him why he'll say I'm paranoid for even looking at his score. He'll also say that its his phone he can do what he want and that whoever it is is his friend.

But I just feel like he's taking more time to talk to someone else instead of me. I don't know how to feel or what to say or where to start