Help with this relationship

So I’ve been knowing this guy for 6 yrs and we’ve been off and on .... the thing is , he lives out of state . He keeps talking about marriage and kids and it’s like , dude I’m only 18 i want to live and experience life. Im too scared to tell him b/c i don’t want him upset but i need to start doing things for me. Maybe we’ll get back together in the future but right now i want to live and i feel like he’s holding me back...

Wtf do i do