Wanting to join the military.

Joining the navy has always been a dream of mine. My boyfriend of almost 3 years (his actually been my best friend for almost 6) gets mad whenever I talk about it. I haven't joined yet because of a few health issues but my brother is joining and it's making me join even more. He always talks about getting married and I told him we could before I went and he's like "well I'm not going to be following you around like an idiot"...made me feel pretty shitty. I know he may just be upset about me leaving but I know I'd follow him if he was joining. I just wanted to see how he feels about it but he always get upset at the topic. Any advice ladies?