I dont think going through gadgets should be any problem if you are not hiding anything but at the same time why will my gf go through my chats. Does that mean she does not trust me.

As for the person that has reduced the calling. It might just be that he is busy or that he was calling frequently at first because he just had her. Now he is back to his normal self. At the same time it can also mean that he is no longer interested. I wish you luck