Marriage!

I'm 16 almost 17. I've been dating this guy for a while now but I've known him for a really long time. I swear, we are soulmates. It's like we're the exact same person with only slight differences. I love this young man with all of my heart and I want to be with him forever. I know it's the honeymoon phase but I also know how life works. He's in the army and he (pretty much but not for real) proposed to me over the phone! He said he wants to marry me as soon as I turn 18 so I can go everywhere with him. I know it sounds mega crazy but is it crazy to seriously consider it..?