Am I crazy for maybe wanting to marry my boyfriend one day? I'm 18

My boyfriend and I have been together since we were 15, we're both 18 now. I seriously feel like he's my other half, we get along so well and can basically understand eachother without even having to say a word. I always feel better when he's around and feel so lucky to have him. He does anything for me, whether it's driving 6 hours in one day to see me for 4 hours or sitting there and comforting me when I'm at my absolute worst. We've matured a lot together. He puts up with a lot and he's so selfless. When I think about the future I see him in it. I don't know if I'm jumping the gun here or not, I really don't want to but I seriously love him to death and don't really want to ever leave his side. He has mentioned kids/marriage a few times during our relationship, starting at about a year of being together. Am I crazy for this?? I'm kind of scared (although I don't think this will happen, but you never know) that thinking like this will end up with me getting my heart broken. Am I being unrealistic? 😕