How do I tell him ?

My boyfriend is into the car scene and is always trying to race, we’ve been together almost 4 years and he wasn’t always like this when we meet he was into cars but not so much racing.. we’re expecting a baby and it scares the living shit out of me when he tells me he’s going to race (him and his friends race for money) I’m happy that he won’t let me near the car at the times of the races because I always want to go and make sure he makes it out ok but that bothers him sometimes. I don’t know how to tell him to stop I’m so paranoid something will happen to him and I’ll have to raise my baby alone but how do I tell him to stop doing something that makes him so happy?