Do you want to be in the Navy or do you want to have the MoD pay for your flying training so you can leave as soon as you have enough experience to be attractive to the airlines?
Training in the military is extremely tough, mentally and physically demanding. If you are not 100% up for it you will struggle. Far from everyone who starts the military flying training makes it to flying fast jets. And if you make it you will be required to remain in the service for at least 5 or 6 years from when you make it to the front line, which is a long time if you dont really want to be there.
If its Boeing you really want, perhaps thats where you should go to start with and leave the Navy to those who really want it.