You’re not his girlfriend, you’re an accessory to his lifestyle.
Running is interesting to only those that run
You don’t do this. What are you getting out of this relationship?
You priorities yourself and leave him to his running, while you enjoy your life and find someone who values you more than a pack mule.
Break his legs
Not even joking
Nice that he’s found his passion. But there are 12 year olds more mature than this guy. He calls YOU selfish? Oh the irony