Advice wanted

I’m 18 years old (my SO is also 18). My boyfriend is going to be enlisting in the marines a little less than a year . We have been together for 4 years now and today we had a long conversation about marriage. I didn’t lie I want to marry him but he wants to get married when I am out of high school (2020) so he can make sure I will always be taken care of god forbid something happened to him. (Knock on wood)

But I’m just scared to get married so young. We’ve lived together for a little over a year now (for family reasons (no kids involved)) so right now not living together would be horrible. Also I can’t live on base unless we are married. I mean willing to share personal information for anyone willing to have a full conversation with me about it.