Orianna Experience Bug?

In my most recent game, I decided to take smite orianna top. 27 minutes into the game, I realized I was level 18 while everyone else was level 13/14. Is this normal? I was ahead and split pushing a lot of the game, but I would have only expected myself to be level 16 at most. Is this a bug involving orianna or something? Sorry I don't have any proof; I didn't think to take any screenshots or videos in game.