Too early?

Me & my boyfriend have been together for about a year n some change, we moved in together & we're basically a married couple. I'm just worried that us being so inseparable at this age (im 18 & his 19) can mess us up in the future, he says it won't because he loves me n he wants to be with me forever, I want the same I just don't want him to want to live his life at the last minute (being single I mean) so what should I do?? I love him so much