I think he might propose?

My boyfriend and I have known each other for 4 years. Have been dating for 1 1/2 years, and have been living together for 8 months. We are both almost 21. He makes me so incredibly happy and we make each other laugh constantly. We’re supportive of each other and I honestly can’t imagine living my life without him. He’s decided to go into the military and I think he’s gonna propose over this family vacation in the mountains. So that we can be engaged before he goes to basic training. I know I’m going to say yes to him whenever he decides to propose, I guess I’m just asking for some advice. The idea of marriage seems like such a huge milestone in your life, but I know I want him to be by my side. I guess I’m just asking for advice, and if anyone else was extremely nervous before your proposal?