I don't think there is cause for concern yet. It might feel like its getting away from you, but its nothing to do with you. Maybe you are reading into his energy and flying high feelings. NRE feelings do make people run away with themselves and those they are with.
I would just watch carefully and let him have at it. It will likely die down in time and settle into a routine. If their NRE starts meaning you get less time, not as much quality time and means there is drama then I would bring it up and start making sure your boundaries are respected.
Anyone want to be friends on Facebook?
Send me your name via PM