What to say to my parents? Please help!

Ever since a friend of mine left after graduation from high school as a Nuke in the Navy, I looked into what he was doing, and found the Navy and the military in general very interesting. Since then, there has not been a day that goes by where I don't think about, or daydream about, being in the Navy. My parents have what I guess would be expectations, that I should stay on track with college, my mom thinking I should be a teacher. But, really, I have no idea what i want to do and my second semester of my sophomore year of college is right around the corner. I feel like I'm wasting my time and my parent's money by going to college with no career in mind. I have a different plan of action. I figured that I would enlist in the Navy as a hospital corpsmen and then, if I want still be a teacher, use my G.I Bill to get through the rest of my college classes. At the moment I'm working on an associates degree that would go towards teaching if I wanted to pick it up later. My parents have never supported my idea of the military and I'm afraid never would. They won't talk to me when I bring it up or say anything positive, just that it's a stupid idea and I'm being influenced by my boyfriend (in DEP currently). I've asked them to see a recruiter, but their convinced that my recruiter will tell me whatever i want to hear. But i trust my recruiter, he's helped 6 people in my graduating class join the military! He actually goes to bat for his soon to be sailors and has told me more downsides of the Navy than most people probably do. He started out by asking me why i wanted to join and then trying to talk me out of it (strange approach). But really, the only thing that scared me was the part of bootcamp where we get vaccinated (I have a terrible fear of needles). I really think i can do this. I am a hands on type of person, a visual learner, by no means a read the chapter and take a test person.
Any advice on what to say to ease the blow when i make my final decision?